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Abstract:

Provided is lithographic printing plates and processes for preparing the
lithographic printing plates having excellent printing durability,
staining resistance and staining resistance over time.
A lithographic printing plate precursor comprising: a substrate; a
photosensitive layer provided on the substrate; and an extra layer
optionally provided between the substrate and the photosensitive layer;
wherein the photosensitive layer or the extra layer adjacent to the
substrate contains (A) a copolymer; and wherein the copolymer (A)
comprises: (a1) a repeating unit having a structure represented by
formula (a1-1) below in a side chain, and (a2) a repeating unit having at
least one of the structures represented by formulae (a2-1) to (a2-6)
below in a side chain. L1 represents a single bond, a divalent
aromatic group containing 6 to 14 carbon atoms, --C(═O)--O--, or
--C(--0)═NR2-- (wherein R2 represents a hydrogen atom,
alkyl or aryl). Z1 represents methylene, ethylene, propylene,
butylene, pentylene, hexylene, heptylene, octylene, cyclohexane-1,4-diyl,
1,2-phenylene, 1,3-phenylene, 1,4-phenylene, 1,2-naphthalene,
1,5-naphthalene and a linking group composed of two or more of these
divalent linking groups linked through --O-- or --S--, wherein a hydrogen
atoms in these divalent linking groups may be replaced by substituents.
R1 represents a hydrogen atom, alkyl, aryl, heterocyclyl, sulfo,
alkylsulfonyl and arylsulfonyl. R21, R22 and R23 each
independently represent a hydrogen atom, halogen atom or C1-8 alkyl.
##STR00001##

Claims:

1. A lithographic printing plate precursor comprising: a substrate; a
photosensitive layer provided on the substrate; and an extra layer
optionally provided between the substrate and the photosensitive layer;
wherein the photosensitive layer or the extra layer adjacent to the
substrate contains (A) a copolymer; and wherein the copolymer (A)
comprises: (a1) a repeating unit having a structure represented by
formula (a1-1) below in a side chain, and (a2) a repeating unit having at
least one of the structure represented by formulae (a2-1) and (a2-2)
below in a side chain; ##STR00156## in formula (a1-1), L1
represents a single bond, a divalent aromatic group containing 6 to 14
carbon atoms, --C(═O)--O--, or --C(═O)--NR2-- (wherein
R2 represents a hydrogen atom, alkyl or aryl); Z1 represents
methylene, ethylene, propylene, butylene, pentylene, hexylene, heptylene,
octylene, cyclohexane-1,4-diyl, 1,2-phenylene, 1,3-phenylene,
1,4-phenylene, 1,2-naphthalene, 1,5-naphthalene and a linking group
composed of two or more of these divalent linking groups linked through
--O-- or --S--, wherein a hydrogen atom in these divalent linking groups
may be replaced by substituents; R1 represents a hydrogen atom,
alkyl, aryl, heterocyclyl, sulfo, alkylsulfonyl and arylsulfonyl;
R21, R22 and R23 each independently represent a hydrogen
atom, halogen atom or C1-8 alkyl; the asterisk (*) indicates the point of
attachment to the main chain of the copolymer; ##STR00157## in formula
(a2-1) or (a2-2), M1 to M4 each independently represent a
hydrogen atom, a metal atom contained in an alkali metal or an alkaline
earth metal or ammonium; Y21 or Y22 represent a single bond, or
a divalent linking group selected from the group consisting of --CO--,
--O--, --NH--, a divalent aliphatic group, a divalent aromatic group and
a combination thereof; and the asterisk (*) indicates the point of
attachment to the main chain of the polymer compound.

2. The lithographic printing plate precursor according to claim 1,
wherein Z1 in formula (a1-1) above is a group selected from group A
below or a combination thereof; (Group A) ##STR00158## in group A,
R52, R53 and R56 each independently represent a hydrogen
atom, halogen atom, hydroxyl, alkoxy, alkyl, aryl or cyano; R56 each
independently represents a halogen atom, hydroxyl, alkoxy, alkyl, aryl or
cyano, n each independently represents an integer of 0 to 4, and m
represents an integer of 0 or 1; if a plurality of R56 groups exist,
they may be identical or different.

3. The lithographic printing plate precursor according to claim 1,
wherein the photosensitive layer contains (B) a polymerization initiator,
(C) a polymerizable compound, (D) a binder and (E) a dye.

4. The lithographic printing plate precursor according to claim 1,
wherein the copolymer (A) is contained in the extra layer.

5. The lithographic printing plate precursor according to claim 1,
wherein Z1 in formula (a1-1) above is a group selected from group B
below or a combination thereof; (Group B) ##STR00159## in group B,
R51 and R52 each independently represent a hydrogen atom,
halogen atom, hydroxyl, alkoxy, alkyl, aryl or cyano.

6. The lithographic printing plate precursor according to claim 1,
wherein Z1 in formula (a1-1) above is C1-14 alkylene, or a divalent
linking group having a linking chain length of 1 to 14 atoms and composed
of two or more alkylenes linked through an oxygen atom linking group
(wherein the alkylenes may each independently be substituted).

8. The lithographic printing plate precursor according to claim 1,
wherein the copolymer (A) further comprises (a3) a repeating unit having
a hydrophilic group in a side chain.

9. The lithographic printing plate precursor according to claim 8,
wherein the hydrophilic group contained in the repeating unit (a3) having
a hydrophilic group in a side chain is a group having a zwitterionic
structure represented by formula (a3-1) or formula (a3-2) below:
##STR00160## in formula (a3-1), R31 and R32 each independently
represent a hydrogen atom, alkyl, alkenyl, alkynyl, aryl, or
heterocyclyl, or R31 and R32 may be joined together to form a
ring structure, L31 represents a linking group, and A represents an
anion-containing structure; Y3 represents a single bond, or a
divalent linking group selected from the group consisting of --CO--,
--O--, --NH--, a divalent aliphatic group, a divalent aromatic group and
a combination thereof; the asterisk (*) indicates the point of attachment
to the main chain of the copolymer; ##STR00161## in formula (a3-2)
above, L32 represents a linking group, and E.sup.+ represents a
cation-containing structure; Y4 represents a single bond, or a
divalent linking group selected from the group consisting of --CO--,
--O--, --NH--, a divalent aliphatic group, a divalent aromatic group and
a combination thereof; the asterisk (*) indicates the point of attachment
to the main chain of the copolymer.

10. The lithographic printing plate precursor according to claim 9,
wherein the group having a zwitterionic structure is represented by
formula (a3-1) above.

12. A process for preparing a lithographic printing plate, comprising:
image-exposing a lithographic printing plate precursor according to claim
1; and developing the exposed lithographic printing plate precursor in
the presence of a developer having a pH of 2 to 14 to remove the
photosensitive layer in unexposed areas.

13. The process for preparing a lithographic printing plate according to
claim 12, comprising forming a protective layer on the surface of the
photosensitive layer opposite to the substrate; wherein the developing
comprises removing the photosensitive layer in unexposed areas and the
protective layer simultaneously in the presence of the developer further
containing a surfactant without including water-washing.

14. The process for preparing a lithographic printing plate according to
claim 12, comprising controlling the pH of the developer at 2.0 to 10.0.

15. A process for preparing a lithographic printing plate, comprising:
image-exposing a lithographic printing plate precursor according to claim
1; and supplying a printing ink and a dampening solution on a printing
press to remove the photosensitive layer in unexposed areas.

16. A copolymer comprising: (a1) a repeating unit having a structure
represented by formula (a1-1) below in a side chain; (a2) a repeating
unit having at least one of the structures represented by formulae
(a2-1), (a2-2), (a2-3), (a2-4), (a2-5) and (a2-6) in a side chain; and
(a3') a repeating unit having a zwitterionic structure represented by
formula (a3-1) or (a3-2) below in a side chain; ##STR00162## in formula
(a1-1), L1 represents a single bond, a divalent aromatic group
containing 6 to 14 carbon atoms, --C(═O)--O--, or
--C(═O)--NR2-- (wherein R2 represents a hydrogen atom,
alkyl or aryl); Z1 represents a divalent linking group selected from
the group consisting of a divalent aliphatic group containing 1 to 14
carbon atoms, a divalent aromatic group containing 6 to 14 carbon atoms,
--NH--, --O--, --S-- and a combination thereof, provided that both ends
are not --NH--, --O-- or --S--, and when L1 is a divalent aromatic
group containing 6 to 14 carbon atoms, Z1 is not a divalent aromatic
group containing 6 to 14 carbon atoms, and the divalent aliphatic group,
divalent aromatic group and --NH-- may have a substituent instead of a
hydrogen atom; R1 represents a hydrogen atom, alkyl, aryl,
heterocyclyl, sulfo, alkylsulfonyl and arylsulfonyl; R21, R22
and R23 each independently represent a hydrogen atom, halogen atom
or C1-8 alkyl; the asterisk (*) indicates the point of attachment to the
main chain of the copolymer; ##STR00163## wherein M1 to M8
each independently represent a hydrogen atom, a metal atom contained in
an alkali metal or an alkaline earth metal or ammonium; R41 to
R46 each independently represent a hydrogen atom or alkyl; Y21
to Y26 represent a single bond, or a divalent linking group selected
from the group consisting of --CO--, --O--, --NH--, a divalent aliphatic
group, a divalent aromatic group and a combination thereof; the asterisk
(*) indicates the point of attachment to the main chain of the polymer
compound; ##STR00164## in formula (a3-1), R31 and R32 each
independently represent a hydrogen atom, alkyl, alkenyl, alkynyl, aryl,
or heterocyclyl, or R31 and R32 may be joined together to form
a ring structure, L31 represents a linking group, and A represents
an anion-containing structure; Y3 represents a single bond, or a
divalent linking group selected from the group consisting of --CO--,
--O--, --NH--, a divalent aliphatic group, a divalent aromatic group and
a combination thereof; the asterisk (*) indicates the point of attachment
to the main chain of the polymer compound; ##STR00165## in formula
(a3-2) above, L32 represents a linking group, and E.sup.+ represents
a cation-containing structure; Y4 represents a single bond, or a
divalent linking group selected from the group consisting of --CO--,
--O--, --NH--, a divalent aliphatic group, a divalent aromatic group and
a combination thereof; the asterisk (*) indicates the point of attachment
to the main chain of the polymer compound.

17. The copolymer according to claim 16, wherein Z1 in the repeating
unit having a structure represented by formula (a1) above is selected
from group A below: (Group A) ##STR00166## in group A, R51 to
R55 each independently represent a hydrogen atom, halogen atom,
hydroxyl, alkoxy, alkyl, aryl or cyano; R56 each independently
represents a halogen atom, hydroxyl, alkoxy, alkyl, aryl or cyano, n each
independently represents an integer of 0 to 4, and m represents an
integer of 0 to 2; if a plurality of R56 groups exist, they may be
identical or different.

18. The copolymer according to claim 16, wherein Z1 in the repeating
unit having a structure represented by formula (a1) above is selected
from group B below: (Group B) ##STR00167## in group B, R51 to
R53 each independently represent a hydrogen atom, halogen atom,
hydroxyl, alkoxy, alkyl, aryl or cyano.

19. The copolymer according to claim 16, wherein the repeating unit (a2)
has a side chain of a structure represented by formula (a2-1) above or
formula (a2-2).

20. The copolymer according to claim 16, wherein the side chain having a
zwitterionic structure in the repeating unit (a3') is a structure
represented by formula (a3-1) above.

21. The copolymer according to claim 16, wherein A.sup.- in formula
(a3-1) above is sulfonate.

22. A process for preparing the copolymer according to claim 16,
comprising introducing the repeating unit (a1) having a structure
represented by formula (a1-1) above in a side chain by reacting a polymer
comprising: (a0) a repeating unit having a structure represented by
formula (a1-0) below in a side chain; (a2) the repeating unit having a
structures represented by any one of formulae (a2-1), (a2-2), (a2-3),
(a2-4), (a2-5) and (a2-6) above in a side chain; and (a3') the repeating
unit having a zwitterionic structure represented by formula (a3-1) or
(a3-2) above in a side chain; with a compound represented by formula
(b-1) or (b-2) below; ##STR00168## in formula (a1-0), L101
represents a single bond, a divalent aromatic group containing 6 to 14
carbon atoms, --C(═O)--O--, or --C(═O)--NR102-- (wherein
R102 represents a hydrogen atom, alkyl or aryl); Z101
represents a divalent linking group selected from the group consisting of
a divalent aliphatic group containing 1 to 14 carbon atoms, a divalent
aromatic group containing 6 to 14 carbon atoms, --NH--, --O--, --S-- and
a combination thereof, provided that both ends are not --NH--, --O-- or
--S--, and when L1 is a divalent aromatic group containing 6 to 14
carbon atoms, Z1 is not a divalent aromatic group containing 6 to 14
carbon atoms, and the divalent aliphatic group, divalent aromatic group
and --NH-- may have a substituent instead of a hydrogen atom; R101
represents a hydrogen atom, alkyl, aryl, heterocyclyl, sulfo,
alkylsulfonyl and arylsulfonyl; the asterisk (*) indicates the point of
attachment to the main chain of the copolymer; ##STR00169## in formulae
(b-1) and (b-2), R111 represents a halogen atom, an optionally
substituted C1-8 alkoxy, or --OSOR112; R112 represents an
optionally substituted C1-8 alkyl; R121 to R129 each
independently represent a hydrogen atom, halogen atom or C1-8 alkyl.

Description:

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application is a continuation of PCT/JP2012/054056
filed on Feb. 21, 2012 and claims priority under 35 U.S.C. §119 of
Japanese Patent Application No. 042496/2011, filed on Feb. 28, 2011,
Japanese Patent Application No. 042497/2011, filed on Feb. 28, 2011, and
Japanese Patent Application No. 013295/2012, filed on Jan. 25, 2012, the
content of which are herein incorporated by reference in their entirety.

FIELD OF THE INVENTION

[0002] The present invention relates to a lithographic printing plate
precursor and a method of manufacturing a lithographic printing plate,
according to which a printing plate is directly manufacturable based on
digital signal output from a computer or the like using various types of
laser, the technique being so-called direct plate making, and
particularly to a lithographic printing plate precursor and a method of
manufacturing planographic a printing plate suitable for simplified
processes.

DESCRIPTION OF THE RELATED ART

[0003] Solid-state laser, semiconductor laser, and gas laser capable of
emitting ultraviolet radiation, visible light and infrared radiation,
over a wavelength range of 300 nm to 1200 nm, have been becoming more
readily available in larger output and smaller size, and these types of
laser are very important as recording light sources in direct plate
making process using digital data output from a computer or the like.
Various recording materials sensitive to these types of laser light have
been investigated. The first category of the materials are those adaptive
to infrared laser recording at an image recording wavelength of 760 nm or
longer, which are exemplified by positive recording material (Patent
Document 1), and negative recording material causing acid-catalyzed
crosslinking (Patent Document 2). The second category of the materials
are those adoptive to ultraviolet or visible light laser recording over
the wavelength range from 300 nm to 700 nm, which are exemplified by
radical-polymerizable negative recording material (Patent. Document 3,
Patent Document 4).

[0004] The conventional lithographic printing plate precursor (also
referred to as "PS plate", hereinafter) have essentially needed, after
exposure for image forming, a process of solubilizing and removing the
non-image-forming area using an aqueous strong alkaline solution
(development process), and have also needed water washing of the
developed printing plate, rinsing with a rinsing solution containing a
surfactant, and post-treatment such as using a desensitization solution
containing gum arabic or a starch derivative. Indispensableness of these
additional wet processes has been a big issue of the conventional PS
plate. This is because, even if the former half of the plate making
process (pattern-wise exposure) may be simplified by virtue of digital
processing, the effect of simplification is limitative so long as the
latter half (development process) relies upon such labor-consuming wet
process.

[0005] In particular in recent years, friendliness to the global
environment has been a great matter of interest across the whole area of
industry, so that issues to be solved from the environmental viewpoint
include use of a developer more close to neutral, and reduction in volume
of waste liquid. Among others, the wet post-treatment have been desired
to be simplified, or replaced with a dry process.

[0006] From this point of view, there has been known methods of
simplifying the post-treatment process, exemplified by single-liquid
treatment or single-bath treatment, by which development and gum solution
are proceeded at the same time. More specifically, they belong to a sort
of simplified development process by which the original plate is exposed
pattern-wise without pre-water washing; removal of a protective layer,
removal of the non-image-forming area, and coating of gum solution are
implemented concomitantly using a single solution or in a single bath;
the original plate is dried without post-water washing, and then put into
the printing process. The lithographic printing plate precursor suitable
for this sort of simplified development, implemented without the
post-water washing, necessarily has a photosensitive layer soluble into a
process solution not so strongly alkaline, and the support thereof
necessarily has a hydrophilic surface in view of improving staining
resistance of the non-image-forming area. However, it was practically
impossible to achieve high printing durability and chemical resistance
with conventional PS plates while satisfying such requirements.

[0007] Thus, lithographic printing plate precursors comprising a
hydrophilic binder polymer layer containing poly(vinyl phosphonic acid)
formed on the surface of a substrate were proposed to satisfy such
requirements (see e.g., Patent Document 5). The precursors were converted
into plates by image-exposing them using a UV laser and then developing
them in a developer at pH 9.8.

[0008] Also, lithographic printing plate precursors obtained by
hydrophilizing a substrate with poly(vinyl phosphonic acid) were proposed
to satisfy such requirements (see e.g., Patent Document 5). The
precursors were converted into plates by image-exposing them using a UV
laser and then developing them in a developer at pH 9.8.

[0009] However, the hydrophilization with poly(vinyl phosphonic acid) or
the like could not achieve enough hydrophilicity to improve staining
resistance, and the resulting plates were insufficient in staining
resistance. As an alternative approach, lithographic printing plate
precursors comprising a layer containing a binder polymer obtained by
copolymerizing a sulfonated monomer and a substrate-adsorbing group
instead of poly(vinyl phosphonic acid) formed on the surface of a
substrate were proposed (see e.g., Patent Document 6), but hydrophilicity
was still insufficient to introduce a hydrophobic polymerizable group for
providing printing durability. Thus, it is very difficult to improve both
printing durability and staining resistance, and any easy-to-handle
lithographic printing plate with good staining resistance and sufficient
printing durability has not been known.

[0010] One approach for simplifying process steps is a method called
on-press development by which exposed lithographic printing plate
precursors are mounted on a cylinder of a printing press and supplied
with a dampening water and an ink while the cylinder is rotated to remove
non-image areas of the lithographic printing plate precursors. In other
words, lithographic printing plate precursors are mounted on a printing
press directly after they are image-exposed so that development is
completed during the normal printing process.

Lithographic printing plate precursors suitable for such on-press
development are required to have not only an image-forming layer soluble
in dampening waters and ink solvents but also lightroom handling
suitability for development on a printing press in a lightroom. However,
it was practically impossible to sufficiently satisfy such requirements
with conventional PS plates. To satisfy such requirements, lithographic
printing plate precursors comprising a photosensitive layer containing
thermoplastic hydrophobic polymer microparticles dispersed in a
hydrophilic binder polymer on a hydrophilic substrate were proposed (see
e.g., Patent Document 7). They were converted into plates by exposing
them to an infrared laser to form an image with the thermoplastic
hydrophobic polymer microparticles coalesced (fused together) by the heat
generated by opto-thermal conversion and then mounting them on a cylinder
of a printing press and supplying at least any one of a dampening water
and an ink to develop the image on press. The lithographic printing plate
precursors are also suitable for handling in a lightroom because the
image is recorded in the infrared region.

[0011] However, the image formed by coalescing (fusing together) the
thermoplastic hydrophobic polymer microparticles is insufficient in
fastness so that the resulting lithographic printing plates are
disadvantageous in printing durability.

[0012] On the other hand, lithographic printing plate precursors
comprising microcapsules incorporating a polymerizable compound instead
of thermoplastic microparticles were proposed (see e.g., Patent Document
8, Patent Document 9, Patent Document 10, Patent Document 11, Patent
Document 12, and Patent Document 13). The lithographic printing plate
precursors according to such proposals have the advantage that the
polymer images formed by a reaction of the polymerizable compound are
superior in fastness to the images formed by coalescence of
microparticles.

Further, it has often been proposed to isolate the polymerizable compound
by using microcapsules because it is highly reactive. Moreover, it has
been proposed to use thermodegradable polymers for the shells of the
microcapsules.

[0013] However, the conventional lithographic printing plate precursors
described in Patent Document 7, JP-A2000-211262, JP-A2001-277740,
JP-A2002-29162, JP-A2002-46361, JP-A2002-137562, and JP-A2002-326470 are
insufficient in the printing durability of the images formed by laser
exposure and should be further improved. Thus, substrates having highly
hydrophilic surfaces were used in these easy-to-handle lithographic
printing plate precursors, with the result that image areas were readily
separated from the substrates with dampening waters during printing and
sufficient printing durability could not be attained. If the substrate
surfaces are hydrophobic, however, inks also deposit on non-image areas
during printing to cause print staining. Thus, it is very difficult to
improve both printing durability and staining resistance, and any
lithographic printing plate precursor suitable for on-press development
with good staining resistance and sufficient printing durability has not
been known.

[0014] On the other hand, lithographic printing plate precursors
comprising a hydrophilic layer with high adhesion to substrate surfaces
to improve both printing durability and staining resistance have been
known. For example, Patent Document 14 discloses a substrate for
lithographic printing plates comprising a hydrophilic layer composed of a
polymer compound directly chemically bound to the surface of the
substrate and having a hydrophilic functional group on the substrate.
Patent Document 15 and Patent Document 16 disclose substrates for
lithographic printing plates comprising an aluminum substrate or
silicated aluminum substrate having a hydrophilic surface to which is
chemically bound a hydrophilic polymer having a reactive group capable of
being chemically bound to the substrate surface directly or through a
moiety having a crosslinking structure. Patent Document 17 discloses a
lithographic printing plate precursor comprising a photosensitive layer
containing a polymerization initiator, a polymerizable compound, and a
binder polymer soluble or swellable in water or aqueous alkaline
solutions on a substrate, wherein the photosensitive layer or an extra
layer contains a copolymer comprising a repeating unitrepeating unit
having at least one ethylenically unsaturated bond and a repeating
unitrepeating unit having at least one functional group interacting with
the substrate surface. Patent Document 18 discloses a lithographic
printing plate precursor comprising a substrate, a hydrophilic layer
formed of a hydrophilic polymer chemically bound to the surface of the
substrate and an image-forming layer in order, wherein the hydrophilic
polymer comprises at least one of a reactive group capable of being
directly chemically bound to the surface of the substrate and a reactive
group capable of being chemically bound to the surface of the substrate
through a crosslinking structure and a positively and negatively charged
substructure.

[0015] Recently, there have been demands for not only improving both
printing durability and staining resistance but also improving staining
resistance even when printing takes place at an interval after
preparation of lithographic printing plates to ensure that the
lithographic printing plates can be easily handled during the printing
process. Thus, not only printing durability and staining resistance but
also staining resistance over time should be improved while striking a
high level balance among them.

[0016] Lithographic printing plate precursors comprising hydrophilic
substrate surfaces have also become known, but it is very difficult to
satisfy all of printing durability, staining resistance, and
developability. This is because the materials used for conventional PS
plates were still insufficient in hydrophilicity so that staining
resistance and developability still remained unsatisfactory. Another
reason for this is because printing durability tends to deteriorate if
the hydrophilicity of the materials is increased to improve staining
resistance and developability.

[0017] For example, Patent Document 19 describes a lithographic printing
plate precursor comprising a substrate having a hydrophilic surface, and
an image-recording layer (photosensitive layer) provided on the substrate
and containing (A) a polymerization initiator, (B) a polymerizable
compound, and (C) a binder polymer soluble or swellable in water or
aqueous alkaline solutions, wherein the photosensitive layer or an extra
layer contains a copolymer comprising at least (a1) a repeating unit
having at least one ethylenically unsaturated band and (a2) a repeating
unit having at least one functional group interacting with the surface of
the substrate. Further, Patent Document 20 describes a substrate for
lithographic printing plates treated with an aqueous solvent comprising
PVPA and an amino-containing compound. Patent Document 21 describes
copolymers composed of a vinyl phosphonic acid, an alkyl (meth)acrylate,
and a tertiary amino-substituted (meth)acrylate. Patent Document 22
describes copolymers for lithographic printing plate precursors
comprising a compound having a functional group X (capable of interacting
with a functional group Y to form a chemical bond and decrease the
contact angle with the substrate surface, such as amino) on the surface
of a substrate.

[0018] On the other hand, there have recently been demands for providing
lithographic printing plate precursors not only striking a high level
balance of printing durability with normal inks, staining resistance, and
developability but also suitable for use with UV inks because UV inks can
be rapidly dried (cured) by UV irradiation, which contributes to high
productivity, and they are solvent-free, therefore
environmentally-friendly, and further they need not be heated so that
they widen the range of applications, etc. However, means for improving
printing durability with UV inks differ from means for improving printing
durability with normal inks, and accordingly, there have been demands for
a method for improving printing durability with UV inks and printing
durability with normal inks simultaneously. Thus, there have been demands
for improving not only printing durability with normal inks, staining
resistance, and developability but also printing durability with UV inks
and achieving a high level balance among them.

[0019][Patent Document 1]
U.S. Pat. No. 4,708,925

[0020][Patent Document 2] JP-A-H8-276558

[0021][Patent Document 3] U.S. Pat. No. 2,850,445

[0022][Patent Document 4]
JP-B-S44-20189

[0023][Patent Document 5] JP-A-2009-98590

[0024] [Patent
Document 6] JP-A-2009-216926

[0025][Patent Document 7] JP Resitration
No. 2938397

[0026][Patent Document 8] JP-A-2000-211262

[0027] [Patent
Document 9] JP-A-2001-277740

[0028][Patent Document 10] JP-A-2002-29162

[0029][Patent Document 11] JP-A-2002-46361

[0030][Patent Document 12]
JP-A-2002-137562

[0031][Patent Document 13] JP-A-2002-326470

[0032][Patent Document 14] JP-A-2001-166491

[0033][Patent Document 15]
JP-A-2003-63166

[0034][Patent Document 16] JP-A-2004-276603

[0035][Patent Document 17] JP-A-2008-213177

[0036][Patent Document 18]
JP-A-2007-118579

[0037][Patent Document 19] JP-A-2006-78999

[0038][Patent Document 20] JP-A-2003-233194

[0039][Patent Document 21]
JP-A-H6-145254

[0040][Patent Document 22] JP-A-2008-265275

SUMMARY OF THE INVENTION

[0041] Under these circumstances, we examined the lithographic printing
plate precursors described in JP-A2001-166491, JP-A2003-63166,
JP-A2004-276603, JP-A2008-213177, and JP-A2007-118579 to find that they
had the disadvantages that staining resistance remained still
insufficient. Especially, they were found to have the disadvantages that
staining resistance decreased especially when printing took place at an
interval after lithographic printing plates were prepared.

[0042] Thus, a first object to be attained by the present invention is to
provide lithographic printing plate precursors that can be converted into
lithographic printing plates having excellent printing durability,
staining resistance and staining resistance over time and processes for
preparing such lithographic printing plates.

[0043] We also examined the lithographic printing plate precursors
described in JP-A2006-78999 to find that they still remained
unsatisfactory because of poor staining resistance due to lack of
hydrophilicity. We also examined the lithographic printing plate
precursors described in JP-A2003-233194 to find that they still remained
unsatisfactory in printing durability with UV inks. Further, we examined
the lithographic printing plate precursors described in JP-A-H6-145254 to
find that they still remained unsatisfactory because of poor staining
resistance due to lack of hydrophilicity. Furthermore, we examined the
lithographic printing plate precursors described in Patent Document 22 to
find that they still remained unsatisfactory in printing durability with
UV inks. Thus, no lithographic printing plate precursor has been known
that achieves a high level balance among printing durability, staining
resistance, and developability as well as printing durability with UV
inks.

[0044] Thus, a second object to be attained by the present invention is to
provide lithographic printing plate precursors that can be converted into
lithographic printing plates having excellent developability, staining
resistance, printing durability with normal inks and printing durability
with UV inks and processes for preparing such lithographic printing
plates.

Means for Solving the Problems

[0045] As a result of careful studies to attain the first object, we found
that printing durability, staining resistance and staining resistance
over time can be improved simultaneously by using a copolymer comprising
a repeating unit having an ethylenically unsaturated group attached to a
side chain through a specific bond and a repeating unit having at least
one functional group interacting with the polymerizable surface of the
substrate.

As a result of careful studies to attain the second object, we found that
staining resistance and developability can be improved by using a
copolymer having a primary or secondary amino-containing side chain in
the photosensitive layer or the primer layer of lithographic printing
plate precursors to confer hydrophilicity and printing durability and
printing durability with UV inks can also be improved by controlling the
linking group other than the amino group of the amino-containing side
chain and the substituent.

[0046] Thus, we found that the objects described above can be attained by
using lithographic printing plate precursors and processes for preparing
lithographic printing plates having the features described below.

The present invention provides the following. [1] A lithographic printing
plate precursor comprising: a substrate; a photosensitive layer provided
on the substrate; and an extra layer optionally provided between the
substrate and the photosensitive layer; wherein the photosensitive layer
or the extra layer adjacent to the substrate contains (A) a copolymer;
and wherein the copolymer (A) comprises: (a1) a repeating unit having a
structure represented by formula (a1-1) below in a side chain, and (a2) a
repeating unit having at least one of the structures represented by
formulae (a2-1), (a2-1), (a2-3), (a2-4), (a2-5) and (a2-6) below in a
side chain.

##STR00002##

In formula (a1-1), L1 represents a single bond, a divalent aromatic
group containing 6 to 14 carbon atoms, --C(═O)--O--, or
--C(═O)--NR2-- (wherein R2 represents a hydrogen atom,
alkyl or aryl). Z1 represents a divalent linking group selected from
the group consisting of a divalent aliphatic group containing 1 to 14
carbon atoms, a divalent aromatic group containing 6 to 14 carbon atoms,
--NH--, --O--, --S-- and a combination thereof, provided that both ends
are not --NH--, --O-- or --S--, and when L1 is a divalent aromatic
group containing 6 to 14 carbon atoms, Z1 is not a divalent aromatic
group containing 6 to 14 carbon atoms, and the divalent aliphatic group,
divalent aromatic group and --NH-- may have a substituent instead of a
hydrogen atom. R1 represents a hydrogen atom, alkyl, aryl,
heterocyclyl, sulfo, alkylsulfonyl and arylsulfonyl. R21, R22
and R23 each independently represent a hydrogen atom, halogen atom
or C1-8 alkyl. The asterisk (*) indicates the point of attachment to the
main chain of the copolymer.

##STR00003##

In formulae (a2-1) to (a2-6), M1 to M8 each independently
represent a hydrogen atom, a metal atom contained in an alkali metal or
an alkaline earth metal or ammonium. R41 to R46 each
independently represent a hydrogen atom or alkyl. Y21 to YZ6
represent a single bond, or a divalent linking group selected from the
group consisting of --CO--, --O--, --NH--, a divalent aliphatic group, a
divalent aromatic group and a combination thereof. The asterisk (*)
indicates the point of attachment to the main chain of the polymer
compound. [2] The lithographic printing plate precursor according to [1],
wherein Z1 in formula (a1-1) above is a group selected from group A
below or a combination thereof.

[0047] (Group A)

##STR00004##

[0048] In group A, R52 to R55 each independently represent a
hydrogen atom, halogen atom, hydroxyl, alkoxy, alkyl, aryl or cyano.
R56 each independently represents a halogen atom, hydroxyl, alkoxy,
alkyl, aryl or cyano, n each independently represents an integer of 0 to
4, and m represents an integer of 0 to 2. If a plurality of R56
groups exist, they may be identical or different.

[3] The lithographic printing plate precursor according to [1] or [2],
wherein the photosensitive layer contains (B) a polymerization initiator,
(C) a polymerizable compound, (D) a binder and (E) a dye. [4] The
lithographic printing plate precursor according to any one of [1] to [3],
wherein the copolymer (A) is contained in the extra layer. [5] The
lithographic printing plate precursor according to any one of [1] to [4],
wherein Z1 in formula (a1-1) above is a group selected from group B
below or a combination thereof.

[0049] (Group B)

##STR00005##

[0050] In group B, R51 to R53 each independently represent a
hydrogen atom, halogen atom, hydroxyl, alkoxy, alkyl, aryl or cyano. [6]
The lithographic printing plate precursor according to any one of [1] to
[5], wherein Z1 in formula (a1-1) above is C1-14 alkylene, or a
divalent linking group having a linking chain length of 1 to 14 atoms and
composed of two or more alkylenes linked through an oxygen atom linking
group (wherein the alkylenes may each independently be substituted).

[7] The lithographic printing plate precursor according to any one of [1]
to [6], wherein the repeating unit (a2) in the copolymer (A) has a side
chain of a structure represented by formula (a2-1) above or formula
(a2-2). [8] The lithographic printing plate precursor according to any
one of [1] to [7], wherein the copolymer (A) further comprises (a3) a
repeating unit having a hydrophilic group in a side chain. [9] The
lithographic printing plate precursor according to [8], wherein the
hydrophilic group contained in the repeating unit (a3) having a
hydrophilic group in a side chain is a group having a zwitterionic
structure represented by formula (a3-1) or formula (a3-2) below:

##STR00006##

In formula (a3-1), R31 and R32 each independently represent a
hydrogen atom, alkyl, alkenyl, alkynyl, aryl, or heterocyclyl, or
R31 and R32 may be joined together to form a ring structure,
L31 represents a linking group, and A- represents an
anion-containing structure. Y3 represents a single bond, or a
divalent linking group selected from the group consisting of --CO--,
--O--, --NH--, a divalent aliphatic group, a divalent aromatic group and
a combination thereof. The asterisk (*) indicates the point of attachment
to the main chain of the copolymer.

##STR00007##

In formula (a3-2) above, L32 represents a linking group, and E.sup.+
represents a cation-containing structure. Y4 represents a single
bond, or a divalent linking group selected from the group consisting of
--CO--, --O--, --NH--, a divalent aliphatic group, a divalent aromatic
group and a combination thereof. The asterisk (*) indicates the point of
attachment to the main chain of the copolymer. [10] The lithographic
printing plate precursor according to [9], wherein the group having a
zwitterionic structure is represented by formula (a3-1) above. [11] The
lithographic printing plate precursor according to [9] or [10], wherein
A- in formula (a3-1) above is sulfonate. [12] A process for preparing a
lithographic printing plate, comprising: image-exposing a lithographic
printing plate precursor according to any one of [1] to [11]; and
developing the exposed lithographic printing plate precursor in the
presence of a developer having a pH of 2 to 14 to remove the
photosensitive layer in unexposed areas. [13] The process for preparing a
lithographic printing plate according to [12], comprising forming a
protective layer on the surface of the photosensitive layer opposite to
the substrate; wherein the developing comprises removing the
photosensitive layer in unexposed areas and the protective layer
simultaneously in the presence of the developer further containing a
surfactant without including water-washin. [14] The process for preparing
a lithographic printing plate according to [12] or [13], comprising
controlling the pH of the developer at 2.0 to 10.0. [15] A process for
preparing a lithographic printing plate, comprising: image-exposing a
lithographic printing plate precursor according to any one of [1] to
[11]; and supplying a printing ink and a dampening solution on a printing
press to remove the photosensitive layer in unexposed areas. [16] A
copolymer comprising: (a1) a repeating unit having a structure
represented by formula (a1-1) below in a side chain; (a2) a repeating
unit having at least one of the structures represented by formulae
(a2-1), (a2-1), (a2-3), (a2-4), (a2-5) and (a2-6) in a side chain; and
(a3') a repeating unit having a zwitterionic structure represented by
formula (a3-1) or (a3-2) below in a side chain.

##STR00008##

In formula (a1-1), L1 represents a single bond, a divalent aromatic
group containing 6 to 14 carbon atoms, --C(═O)--O--, or
--C(═O)--NR2-- (wherein R2 represents a hydrogen atom,
alkyl or aryl). Z1 represents a divalent linking group selected from
the group consisting of a divalent aliphatic group containing 1 to 14
carbon atoms, a divalent aromatic group containing 6 to 14 carbon atoms,
--NH--, --O--, --S-- and a combination thereof, provided that both ends
are not --NH--, --O-- or --S--, and when L1 is a divalent aromatic
group containing 6 to 14 carbon atoms, Z1 is not a divalent aromatic
group containing 6 to 14 carbon atoms, and the divalent aliphatic group,
divalent aromatic group and --NH-- may have a substituent instead of a
hydrogen atom. R1 represents a hydrogen atom, alkyl, aryl,
heterocyclyl, sulfo, alkylsulfonyl and arylsulfonyl. R21, R22
and R23 each independently represent a hydrogen atom, halogen atom
or C1-8 alkyl. The asterisk (*) indicates the point of attachment to the
main chain of the copolymer.

##STR00009##

wherein M1 to M8 each independently represent a hydrogen atom,
a metal atom contained in an alkali metal or an alkaline earth metal or
ammonium. R41 to R46 each independently represent a hydrogen
atom or alkyl. Y21 to Y26 represent a single bond, or a
divalent linking group selected from the group consisting of --CO--,
--O--, --NH--, a divalent aliphatic group, a divalent aromatic group and
a combination thereof. The asterisk (*) indicates the point of attachment
to the main chain of the polymer compound.

##STR00010##

In formula (a3-1), R31 and R32 each independently represent a
hydrogen atom, alkyl, alkenyl, alkynyl, aryl, or heterocyclyl, or
R31 and R32 may be joined together to form a ring structure,
L31 represents a linking group, and A- represents an
anion-containing structure. Y3 represents a single bond, or a
divalent linking group selected from the group consisting of --CO--,
--O--, --NH--, a divalent aliphatic group, a divalent aromatic group and
a combination thereof. The asterisk (*) indicates the point of attachment
to the main chain of the polymer compound.

##STR00011##

In formula (a3-2) above, L32 represents a linking group, and E.sup.+
represents a cation-containing structure. Y4 represents a single
bond, or a divalent linking group selected from the group consisting of
--CO--, --O--, --NH--, a divalent aliphatic group, a divalent aromatic
group and a combination thereof. The asterisk (*) indicates the point of
attachment to the main chain of the polymer compound. [17] The copolymer
according to [16], wherein Z1 in the repeating unit having a
structure represented by formula (a1) above is selected from group A
below:

##STR00012##

In group A, R51 to R55 each independently represent a hydrogen
atom, halogen atom, hydroxyl, alkoxy, alkyl, aryl or cyano. R56 each
independently represents a halogen atom, hydroxyl, alkoxy, alkyl, aryl or
cyano, n each independently represents an integer of 0 to 4, and m
represents an integer of 0 to 2. If a plurality of R56 groups exist,
they may be identical or different.

[0051] The copolymer according to [16] or [17], wherein Z1 in the
repeating unit having a structure represented by formula (a1) above is
selected from group B below:

[0052] (Group B)

##STR00013##

In group B, R51 to R53 each independently represent a hydrogen
atom, halogen atom, hydroxyl, alkoxy, alkyl, aryl or cyano. [19] The
copolymer according to any one of [16] to [18], wherein the repeating
unit (a2) has a side chain of a structure represented by formula (a2-1)
above or formula (a2-2). [20] The copolymer according to any one of [16]
to [19], wherein the side chain having a zwitterionic structure in the
repeating unit (a3') is a structure represented by formula (a3-1) above.
[21] The copolymer according to any one of [16] to [20], wherein A- in
formula (a3-1) above is sulfonate. [22] A process for preparing the
copolymer according to any one of [16] to [21], comprising introducing
the repeating unit (a1) having a structure represented by formula (a1-1)
above in a side chain by reacting a polymer comprising: (a0) a repeating
unit having a structure represented by formula (a1-0) below in a side
chain; (a2) the repeating unit having a structures represented by any one
of formulae (a2-1), (a2-1), (a2-3), (a2-4), (a2-5) and (a2-6) above in a
side chain; and (a3') the repeating unit having a zwitterionic structure
represented by formula (a3-1) or (a3-2) above in a side chain; with a
compound represented by formula (b-1) or (b-2) below.

##STR00014##

In formula (a1-0), L101 represents a single bond, a divalent
aromatic group containing 6 to 14 carbon atoms, --C(═O)--O--, or
--C(═O)--NR102-- (wherein R102 represents a hydrogen atom,
alkyl or aryl). Z101 represents a divalent linking group selected
from the group consisting of a divalent aliphatic group containing 1 to
14 carbon atoms, a divalent aromatic group containing 6 to 14 carbon
atoms, --NH--, --O--, --S-- and a combination thereof, provided that both
ends are not --NH--, --O-- or --S--, and when L1 is a divalent
aromatic group containing 6 to 14 carbon atoms, Z1 is not a divalent
aromatic group containing 6 to 14 carbon atoms, and the divalent
aliphatic group, divalent aromatic group and --NH-- may have a
substituent instead of a hydrogen atom. R101 represents a hydrogen
atom, alkyl, aryl, heterocyclyl, sulfo, alkylsulfonyl and arylsulfonyl.
The asterisk (*) indicates the point of attachment to the main chain of
the copolymer.

##STR00015##

In formulae (b-1) and (b-2), R111 represents a halogen atom, an
optionally substituted C1-8 alkoxy, or --OSOR112. R112
represents an optionally substituted C1-8 alkyl. R121 to R129
each independently represent a hydrogen atom, halogen atom or C1-8 alkyl.
[23] A lithographic printing plate precursor comprising: a substrate; a
photosensitive layer provided on the substrate and containing at least
(B) a polymerization initiator, (C) a polymerizable compound and (D) a
binder; and an extra layer optionally provided between the substrate and
the photosensitive layer; wherein the photosensitive layer or the extra
layer adjacent to the substrate contains (A) a copolymer different from
(D) the binder and containing a compound comprising (a0) a repeating unit
having a structure represented by formula (a1-0) below in a side chain.

##STR00016##

In formula (a1-0), L1 represents a divalent covalent linking group,
excluding alkylene. Z1 represents a covalent linking group selected
from the group consisting of alkylene, arylene, --O--, --S-- and a
combination thereof, provided that both ends are not --O-- or --S--, and
when L1 is arylene, Z1 is not arylene. X1 represents a
hydrogen atom or an electron-releasing group having a Hammett substituent
constant op value of 0.2 or less. The asterisk (*) indicates the point of
attachment to the main chain of the copolymer. [24] The lithographic
printing plate precursor according to [23], wherein Z1 in formula
(a1-0) above represents a linking group selected from the group
consisting of alkylene, arylene, --O-- and a combination thereof,
provided that --O--is not terminal. [25] The lithographic printing plate
precursor according to [23] or [24], wherein X1 in formula (a1-0)
above represents a hydrogen atom, alkyl, aryl or heterocyclyl. [26] The
lithographic printing plate precursor according to any one of [23] to
[25], wherein the copolymer (A) comprises (a2) a repeating unit having at
least one functional group interacting with the substrate surface. [27]
The lithographic printing plate precursor according to any one of [23] to
[26], wherein the copolymer (A) comprises (a1) a repeating unit having a
structure represented by formula (a1-1) below in a side chain.

##STR00017##

In formula (a1-1), L2 represents a divalent covalent linking group,
excluding alkylene. Z2 represents a covalent linking group selected
from the group consisting of alkylene, arylene, --O--, --S-- and a
combination thereof, provided that --O-- and --S-- are not terminal, and
when L1 is arylene. Z1 is not arylene. X2 represents a
hydrogen atom or an electron-releasing group having a Hammett substituent
constant op value of 0.2 or less. R represents a substituent. The
asterisk (*) indicates the point of attachment to the main chain of the
copolymer. [28] The lithographic printing plate precursor according to
[27], wherein R in formula (a1-1) above is a radically polymerizable
reactive group. [29] The lithographic printing plate precursor according
to any one of [26] to [28], wherein the functional group interacting with
the substrate surface contained in (a2) the repeating unit having at
least one functional group interacting with the substrate surface is
selected from a phosphoric acid ester or a salt thereof, or a phosphonic
acid or a salt thereof. [30] The lithographic printing plate precursor
according to any one of [23] to [29], wherein the extra layer is a primer
layer provided between the substrate and the photosensitive layer. [31]
The lithographic printing plate precursor according to any one of [23] to
[30], wherein the copolymer (A) comprises (a3) a repeating unit having a
hydrophilic group in a side chain. [32] The lithographic printing plate
precursor according to [31], wherein the hydrophilic group contained in
(a3) the repeating unit having a hydrophilic group in a side chain is
selected from a zwitterionic structure represented by formula (a3-1) or
formula (a3-2) below.

##STR00018##

In formula (a3-1), R31 and R32 each independently represent a
hydrogen atom, alkyl, alkenyl, alkynyl, aryl or heterocyclyl, or R31
and R32 may be joined together to form a ring structure, and
L31 represents a divalent linking group. A.sup.- represents an
anion-containing structure. Y3 represents a single bond, or a
divalent linking group selected from the group consisting of --CO--,
--O--, --NH--, a divalent aliphatic group, a divalent aromatic group and
a combination thereof. The asterisk (*) indicates the point of attachment
to the main chain of the copolymer.

##STR00019##

In formula (a3-2), L32 represents a divalent linking group, and
represents a cation-containing structure. Y4 represents a single
bond, or a divalent linking group selected from the group consisting of
--CO--, --O--, --NH--, a divalent aliphatic group, a divalent aromatic
group and a combination thereof. The asterisk (*) indicates the point of
attachment to the main chain of the copolymer. [33] The lithographic
printing plate precursor according to any one of [27] to [32], wherein
(a1) the repeating unit having a structure represented by formula (a1-1)
in a side chain in the copolymer (A) was obtained by a substitution
reaction of the hydrogen atom attached to the nitrogen atom attached to
X1 and Z1 of (a0) the repeating unit having a structure
represented by formula (a1-0) in a side chain. [34] The lithographic
printing plate precursor according to any one of [23] to [33], comprising
a protective layer on the surface of the photosensitive layer opposite to
the substrate. [35] A process for preparing a lithographic printing
plate, comprising: image-exposing a lithographic printing plate precursor
according to any one of [23] to [33]; and developing the exposed
lithographic printing plate precursor in a developer containing a
surfactant; wherein the developing comprises removing unexposed areas of
the photosensitive layer and the protective layer simultaneously in the
presence of the developer. [36] The process for preparing a lithographic
printing plate according to [35], wherein the developing comprises
removing unexposed areas of the photosensitive layer and the protective
layer simultaneously in the presence of the developer without including
water-washing. [37] The process for preparing a lithographic printing
plate according to [35] or [36], wherein the exposing comprises exposure
using a laser light having a wavelength of 350 nm to 450 nm. [38] The
process for preparing a lithographic printing plate according to any one
of [35] to [37], comprising controlling the pH of the developer at 2.0 to
10.0. [39] The process for preparing a lithographic printing plate
according to any one of [35] to [38], wherein the developer contains
carbonate ions and bicarbonate ions.

Advantages of the Invention

[0053] According to a first feature of the present invention, lithographic
printing plates having excellent printing durability, staining resistance
and staining resistance over time can be provided as well as processes
for preparing such lithographic printing plates. According to a second
feature of the present invention, lithographic printing plate precursors
that can be converted into lithographic printing plates having excellent
developability, handling properties, printing durability with normal inks
and printing durability with UV inks can be provided as well as processes
for preparing such lithographic printing plates.

BRIEF DESCRIPTION OF THE DRAWINGS

[0054] FIG. 1 is an explanatory drawing illustrating an exemplary
configuration of an automatic processor; and

[0055] FIG. 2 is an explanatory drawing illustrating another exemplary
configuration of the automatic processor.

THE BEST MODES FOR CARRYING OUT THE INVENTION

[0056] The present invention will be explained in detail below. The
description of essential features below may be sometimes based on
representative embodiments of the present invention, but the present
invention is not limited to such embodiments. As used herein, the
numerical ranges expressed with "to" are used to mean the ranges
including the values indicated before and after "to" as lower and upper
limits.

As used herein, any reference to a group in a compound represented by a
formula without indicating that the group is substituted or unsubstituted
includes the group not only unsubstituted but also substituted if the
group may be further substituted, unless otherwise specified. For
example, the reference in a formula that "R represents alkyl, aryl or
heterocyclyl" means that "R represents unsubstituted alkyl, substituted
alkyl, unsubstituted aryl, substituted aryl, unsubstituted heterocyclyl
or substituted heterocyclyl". As used herein, "(meth)acrylamide" refers
to the concept including both methacrylamide and acrylamide. As used
herein, the term "printing durability" refers to printing durability with
normal inks, unless otherwise specified.

First Embodiment

Lithographic Printing Plate Precursor

[0057] A lithographic printing plate precursor according to a first
embodiment of the present invention is explained in detail below. The
lithographic printing plate precursor of the present invention comprises
a substrate, a photosensitive layer provided on the substrate, and an
extra layer optionally provided between the substrate and the
photosensitive layer; wherein the photosensitive layer or the extra layer
adjacent to the substrate contains (A) a copolymer, and wherein the
copolymer (A) comprises (a1) a repeating unit having a structure
represented by formula (a1-1) below in a side chain, and (a2) a repeating
unit having at least one of the structures represented by formulae (a2-1)
(a2-1) (a2-3), (a2-4), (a2-5) and (a2-6) below in a side chain.

##STR00020##

In formula (a1-1), L1 represents a single bond, a divalent aromatic
group containing 6 to 14 carbon atoms, --C(═O)--O--, or
--C(═O)--NR2-- (wherein R2 represents a hydrogen atom,
alkyl or aryl). Z1 represents a divalent linking group selected from
the group consisting of a divalent aliphatic group containing 1 to 14
carbon atoms, a divalent aromatic group containing 6 to 14 carbon atoms,
--NH--, --O--, --S-- and a combination thereof, provided that both ends
are not --NH--, --O-- or --S--, and when L1 is a divalent aromatic
group containing 6 to 14 carbon atoms, Z1 is not a divalent aromatic
group containing 6 to 14 carbon atoms, and the divalent aliphatic group,
divalent aromatic group and --NH-- may have a substituent instead of a
hydrogen atom. R represents a hydrogen atom, alkyl, aryl, heterocyclyl,
sulfo, alkylsulfonyl and arylsulfonyl. R21, R22 and R23
each independently represent a hydrogen atom, halogen atom or C1-8 alkyl.
The asterisk (*) indicates the point of attachment to the main chain of
the copolymer.

##STR00021##

In formulae (a2-1) to (a2-6), M1 to M8 each independently
represent a hydrogen atom, a metal atom contained in an alkali metal or
an alkaline earth metal or ammonium. R41 to R46 each
independently represent a hydrogen atom or alkyl. Y21 to Y26
represent a single bond, or a divalent linking group selected from the
group consisting of --CO--, --O--, --NH--, a divalent aliphatic group, a
divalent aromatic group and a combination thereof. The asterisk (*)
indicates the point of attachment to the main chain of the polymer
compound. The copolymer (A) comprising (a1) a repeating unit having a
structure represented by formula (a1-1) below in a side chain, and (a2) a
repeating unit having at least one of the structures represented by
formulae (a2-1), (a2-1), (a2-3), (a2-4), (a2-5) and (a2-6) below in a
side chain is hereinafter also referred to as a specific polymer
compound.

[0058] Without being bound to any theory, it is assumed that the
advantages of the present invention can be achieved by the lithographic
printing plate precursor of the present invention containing the
copolymer (A) in the photosensitive layer or the extra layer (preferably
a primer layer between the substrate and the photosensitive layer) for
the following reasons. Polymers having a structure represented by (a1-1)
above in a side chain exhibit strong and high adhesion by radical
polymerization of the compound in the photosensitive layer and a
(meth)acrylamide group. Further, non-image areas (unexposed areas) can be
prevented from adhering to the photosensitive layer after development and
can be provided with a substrate surface having unprecedentedly high
hydrophilicity because of the hydrophilicity of the (meth)acrylamide
group and the presence of a spacer selected from a specific group
hindering electrostatic interaction with the photosensitive layer
especially in the point of attachment of polymerizable groups to the main
chain where electrostatic interaction with the photosensitive layer
otherwise would be liable to occur. This may contribute to the
achievement of the objects of the present invention, i.e., lithographic
printing plate precursors that can be converted into lithographic
printing plates having very excellent staining resistance and stability
over time and excellent printing durability (more preferably, also having
excellent developability) can be provided as well as processes for
preparing such lithographic printing plates.

Moreover, the copolymer (A) having a structure represented by formula
(a1-1) can be synthesized by using a polymer having an amine structure in
a side chain as exemplified by formula (a1-0) as a precursor. Amine
compounds typically have high nucleophilic reactivity, which allows a
desired reaction to be performed even in protic solvents. Thus,
polymerizable groups can be introduced into polymers in protic solvents
by taking advantage of the reactivity of amine structures even if the
polymers have low solubility in aprotic solvents and high solubility in
protic solvents such as alcohols, water and the like, with the result
that very highly hydrophilic polymers having a radically polymerizable
group can be synthesized.

[0059] Preferably, the lithographic printing plate precursor of the
present invention can be directly converted into a plate using various
lasers from digital signals of computers or the like, i.e., it is
applicable to so-called computer-to-plate. Preferably, it can also be
developed in aqueous solutions at pH 2.0 to 10.0 or less or on a printing
press.

[0060] Preferred aspects of the lithographic printing plate precursor of
the present invention are explained in detail below.

[0061] The lithographic printing plate precursor of the present invention
comprises a substrate and a photosensitive layer provided on the
substrate.

Further, the lithographic printing plate precursor of the present
invention may optionally comprise an extra layer between the substrate
and the photosensitive layer. The lithographic printing plate precursor
of the present invention preferably comprises a primer layer as the extra
layer. Further, the lithographic printing plate precursor of the present
invention preferably comprises a protective layer on the surface of the
photosensitive layer opposite to the substrate. Further, the lithographic
printing plate precursor of the present invention may comprise a back
coating layer on the bottom of the substrate as appropriate. The
photosensitive layer, extra layer, protective layer, and back coating
layer constituting the lithographic printing plate precursor of the
present invention are explained in order below, and processes for forming
the lithographic printing plate precursor of the present invention are
also explained.

[0062] <Photosensitive Layer>

The photosensitive layer of the lithographic printing plate precursor of
the present invention preferably contains (B) a polymerization initiator,
(C) a polymerizable compound, (D) a binder and (E) a dye. Further, the
lithographic printing plate precursor of the present invention is
characterized in that the photosensitive layer or the extra layer
contains (A) a copolymer and that the copolymer (A) comprises (a1) a
repeating unit having a structure represented by formula (a1-1) in a side
chain, and (a2) a repeating unit having at least one of the structures
represented by formulae (a2-1), (a2-1), (a2-3), (a2-4), (a2-5) and (a2-6)
in a side chain. Thus, the photosensitive layer may contain the copolymer
(A). When the primer layer described below is provided as the extra layer
between the substrate and the photosensitive layer, the photosensitive
layer may not contain the copolymer (A), but the primer layer may contain
the copolymer (A). However, the primer layer preferably contains the
copolymer (A) in the lithographic printing plate precursor of the present
invention. It should be noted that the copolymer (A) differs from the
binder (D). Further, the photosensitive layer may further contain other
components as appropriate.

[0063] The components of the photosensitive layer are explained in detail
below.

[0064] (A) Copolymer

In the lithographic printing plate precursor of the present invention,
the photosensitive layer adjacent to the substrate may contain (A) a
copolymer comprising a (a1) a repeating unit having a structure
represented by formula (a1-1) below in a side chain and (a2) a repeating
unit having at least one of the structures represented by formulae (a2-1)
to (a2-6) in a side chain. Although the primer layer preferably contains
the copolymer (A) in the lithographic printing plate precursor of the
present invention, the copolymer (A) (specific polymer compound) is
described in detail below in the photosensitive layer for sake of
explanation.

[0069] L1 is preferably a single bond, a divalent aromatic group, or
L5 or L6 shown above. To improve staining resistance, L1 is
preferably L5 or L6 defined above, more preferably L5.

[0070] In formula (a1-1) above, the divalent linking group represented by
Z1 refers to a divalent linking group selected from the group
consisting of a divalent aliphatic group containing 1 to 14 carbon atoms,
a divalent aromatic group containing 6 to 14 carbon atoms, --NH--, --O--,
--S-- and a combination thereof, provided that both ends are not --NH--,
--O-- or --S--, and when L1 is a divalent aromatic group containing
6 to 14 carbon atoms, Z1 is not a divalent aromatic group containing
6 to 14 carbon atoms, and the divalent aliphatic group, divalent aromatic
group and --NH-- may have a substituent instead of a hydrogen atom.

[0071] The divalent aliphatic group preferably has a chain structure to a
ring structure, more preferably has a straight-chain structure to a
branched chain structure. The divalent aliphatic group preferably
contains 1 to 20, more preferably 1 to 15, even more preferably 1 to 12,
especially preferably 1 to 10 carbon atoms.

Examples of substituents on the divalent aromatic group include the
examples of substituents on the divalent aliphatic group listed above, as
well as alkyl.

[0073] In the lithographic printing plate precursor of the present
invention, the divalent linking group represented by Z1 in formula
(a1-1) above is preferably a group selected from group A or a combination
thereof.

[0074] (Group A)

##STR00023##

[0075] In group A, R51 to R55 each independently represent a
hydrogen atom, halogen atom, hydroxyl, alkoxy, alkyl, aryl or cyano.
R56 each independently represents a halogen atom, hydroxyl, alkoxy,
alkyl, aryl or cyano, n represents an integer of 0 to 4, and m represents
an integer of 0 to 2. If a plurality of R56 groups exist, they may
be identical or different.

[0076] A highly hydrophilic substrate surface can be provided by using a
combination of divalent linking groups selected from group A because the
absence of carbonyl in the so-called spacer Z1 in formula (a1-1)
above hinders interaction with the photosensitive layer, thereby
preventing development failure and improving staining resistance.

[0077] More preferably, Z1 in formula (a1-1) above is a group
selected from group B below or a combination thereof to improve the
hydrophilicity of the spacer itself.

[0078] (Group B)

##STR00024##

In group B, R51 to R53 each independently represent a hydrogen
atom, halogen atom, hydroxyl, alkoxy, alkyl, aryl or cyano. In group B
above, R51 to R53 have the same meanings as defined for
R51 to R53 in group A, and also cover similar preferred ranges.

[0079] For similar reasons, Z1 in formula (a1-1) above is especially
preferably a group selected from group C or a combination thereof.

[0080] (Group C)

##STR00025##

In group C, R52 and R53 each independently represent a hydrogen
atom, halogen atom, hydroxyl, alkoxy, alkyl, aryl or cyano. In group B
above, R52 and R53 have the same meanings as defined for
R52 and R53 in group A, and also cover similar preferred
ranges. In formula (a1-1) above, the structure represented by Z1 is
preferably methylene, ethylene, propylene, butylene, pentylene, hexylene,
heptylene, octylene, cyclohexane-1,4-diyl, 1,2-phenylene, 1,3-phenylene,
1,4-phenylene, 1,2-naphthalene, 1,5-naphthalene and a linking group
composed of two or more of these divalent linking groups linked through
--O-- or --S--, more preferably methylene, ethylene, propylene, butylene,
pentylene, hexylene, 1,3-phenylene, 1,4-phenylene, 1,5-naphthalene and a
linking group composed of two or more of these divalent linking groups
linked through --O--. Specifically, the following structures are
included, but the present invention is not limited to these examples.
Methylene, ethylene, propylene, butylene, pentylene, 1,4-phenylene,
--C2H4--O--C2H4--,
--C2H4--O--C2H4--O--C2H4--,
--C2H4--O--C2H4--O--C2H4--O--C2H4-
--, --C3H6--O--C2H4--O--C2H4--O--C3H.su-
b.6--, --CH2--C≡C--CH2--,
--CH2-cyclohexane-1,4-diyl-CH2--,
1,4-phenylene-O-1,4-phenylene-O-1,4-phenylene-,
--C2H4--O-1,4-phenylene-O-1,4-phenylene-O--C2H4--,
--CH2-1,4-phenylene-CH2--,
--C2H4--S--C2H4--,
--C2H4--NH--C2H4--NH--C2H4--,
--CH(OH)--CH(OH)--. Moreover, the hydrogen atoms in these groups may be
replaced by substituents. Among them, the structure represented by
Z1 in formula (a1-1) above is preferably C1-14 alkylene, or a
divalent linking group having a linking chain length of 1 to 14 atoms and
contains two or more alkylenes linked through an oxygen atom linking
group wherein the alkylenes may each independently have a substituent.
The divalent linking group having a linking chain length of 1 to 14 atoms
and containing two or more alkylenes linked through an oxygen atom
linking group is preferably an ethylene oxide chain, a propylene oxide
chain, and a combination thereof.

[0082] The alkyl refers to a straight-chain, branched chain, or cyclic
substituted or unsubstituted alkyl. Examples include alkyl (preferably
C1-30 alkyl, e.g., methyl, ethyl, n-propyl, isopropyl, t-butyl, n-octyl,
eicosyl, 2-chloroethyl, 2-cyanoethyl, 2-ethylhexyl), cycloalkyl
(preferably a substituted or unsubstituted C3-30 cycloalkyl, e.g.,
cyclohexyl, cyclopentyl, 4-n-dodecylcyclohexyl), bicycloalkyl (preferably
a substituted or unsubstituted C5-30 bicycloalkyl, i.e., a monovalent
group obtained by removing one hydrogen atom from a C5-30 bicycloalkane;
e.g., bicyclo[1,2,2]heptane-2-yl, bicyclo[2,2,2]octane-3-yl), as well as
tricyclo structure containing more ring structures and the like. It
should be noted that the alkyls in the substituents explained below
(e.g., alkyl in alkylthio) also refer to such a category of alkyls. The
aryl preferably refers to a substituted or unsubstituted C6-30 aryl,
e.g., phenyl, p-tolyl, nephthyl, m-chlorophenyl,
o-hexadecanoylaminophenyl.

The heterocyclyl is preferably a monovalent group obtained by removing
one hydrogen atom from a substituted or unsubstituted 5- or 6-membered
aromatic or non-aromatic heterocyclic compound, even more preferably a 5-
or 6-membered aromatic heterocyclyl containing 3 to 30 carbon atoms. For
example, 2-furyl, 2-thienyl, 2-pyrimidinyl, and 2-benzothiazolyl are
preferred. The sulfo, alkylsulfonyl and arylsulfonyl are preferably a
substituted or unsubstituted C1-30 alkylsulfonyl, and a substituted or
unsubstituted C6-30 arylsulfonyl, e.g., methylsulfonyl, ethylsulfonyl,
phenylsulfonyl, p-methylphenylsulfonyl.

[0083] In formula (a1-1) above, R1 is preferably a hydrogen atom, an
optionally substituted alkyl, aryl and heterocyclyl, more preferably a
hydrogen atom, an optionally substituted alkyl and aryl, especially
preferably a hydrogen atom or methyl, more especially preferably a
hydrogen atom.

[0084] In formula (a1-1) above, R21, R22 and R23 each
independently represent a hydrogen atom, halogen atom or C1-8 alkyl.
Preferably, R21, R22 and R23 each independently represent
a hydrogen atom, C1-6 alkyl or halogen atom (--F, --Br, --Cl, --I). More
preferably, at least two of R21, R22 and R23 are a
hydrogen atom, and the remaining one is a hydrogen atom or C1-6 alkyl.
Especially preferably, at least two of R21, R22 and R23
are a hydrogen atom, and the remaining one is a hydrogen atom or methyl.

[0085] Specific examples of structures represented by formula (a1-1) above
in the present invention are shown below, but the present invention is
not limited to these examples.

##STR00026## ##STR00027## ##STR00028## ##STR00029## ##STR00030##

[0086] The repeating unit (a1) having a structure represented by formula
(a1-1) in a side chain includes (meth)acrylic polymers, styryl polymers,
polyurethane resins, polyvinyl alcohol resins, polyvinyl formal resins,
polyamide resins, polyester resins, epoxy resins and the like.
Especially, (meth)acrylic polymers, and styryl polymers are preferred,
more preferably (meth)acrylic polymers. The repeating unit (a1) having a
structure represented by formula (a1-1) in a side chain is preferably a
repeating unit represented by formula (A1) below:

##STR00031##

[0087] In formula (A1), Ra to Rc each independently represent a
hydrogen atom, C1-6 alkyl or halogen atom. The repeating unit (a1)
represents a structure represented by formula (a1-1) above, and is
attached to a carbon atom on the main chain of formula (A1) at the point
indicated by the asterisk (*) in formula (a1-1) above.

[0088] In the specific polymer compound of the present invention, the
proportion of the repeating unit (a1) having a structure represented by
formula (a1-1) above is preferably in the range of 1 to 99 mol %, more
preferably in the range of 1 to 90 mol %, even more preferably in the
range of 1 to 80 mol % based on the total repeating units to improve
staining resistance and developability.

[0089] Preferably, the unit having a structure represented by formula
(a1-1) above has a structure generated by the action of a reactive
reagent on a polymer containing a repeating unit represented by the
formula below in a side chain. The structure of formula (a1-1) above can
readily be obtained by the action of a reactive reagent such as, e.g., an
acid halide, acid anhydride, mixed acid anhydride, isocyanic acid
compound, epoxy compound, sulfonyl halide compound or alkyl halide
compound or the like on the structure represented by formula (a1-0)
above.

##STR00032##

In the formula above, L1, Z1 and R1 have the same meanings
as defined for L-, Z1 and R1 in formula (a1-1) above.

[0090] The reactive reagent is preferably a compound of formula (b-1) or
formula (b-2) below.

##STR00033##

In formula (b-1) and formula (b-2), R111 represents a halogen atom,
an optionally substituted C1-8 alkoxy, or --OSOR112. R112
represents an optionally substituted C1-8 alkyl. R121 to R129
each independently represent a hydrogen atom, halogen atom or C1-8 alkyl.
Preferably, R111 is a C3-8 alkoxy or halogen atom, more preferably a
halogen atom because of the reactivity with the primary or secondary
amino group in formula (a1-1). Preferably, R112 is C1-5 alkyl, more
preferably C1-3 alkyl. Preferably, R121 to R129 each
independently represent a hydrogen atom, or C1-3 alkyl, more preferably a
hydrogen atom, or methyl.

[0091] The reaction with formula (b-1) or formula (b-2) can be performed
in not only aprotic solvents but also protic solvents because of high
reactivity of the amino group. To promote the reaction, a catalyst may be
used as appropriate. The catalyst used may be any one that activates the
amino group or formula (b-1) or formula (b-2).

[0092] (a2) Repeating unit having at least one functional group
interacting with the substrate surface:

The copolymer (A) is characterized in that it comprises (a2) a repeating
unit having at least one of the structures represented by formulae
(a2-1), (a2-2), (a2-3), (a2-4), (a2-5) and (a2-6) below in a side chain
(hereinafter also referred to as a "repeating unit having at least one
functional group interacting with the substrate surface).

##STR00034##

In formulae (a2-1) to (a2-6), M1 to M8 each independently
represent a hydrogen atom, a metal atom contained in an alkali metal or
an alkaline earth metal or ammonium. R41 to R46 each
independently represent a hydrogen atom or alkyl. Y21 to Y26
represent a single bond, or a divalent linking group selected from the
group consisting of --CO--, --O--, --NH--, a divalent aliphatic group, a
divalent aromatic group and a combination thereof. The asterisk (*)
indicates the point of attachment to the main chain of the polymer
compound.

[0093] In the formulae above, R41 to R46 preferably each
independently represent a hydrogen atom or C1-10 alkyl. The alkyls
represented by R41 to R46 include methyl, ethyl, propyl, octyl,
isopropyl, t-butyl, isopentyl, 2-ethylhexyl, 2-methylhexyl, cyclopentyl
and the like.

[0094] In the formulae above, Y21 to Y26 each independently
represent a single bond, or a divalent linking group selected from the
group consisting of --CO--, --O--, --NH--, a divalent aliphatic group, a
divalent aromatic group and a combination thereof.

[0095] Specific examples of Y21 to Y26 consisting of the
combinations described above are shown below. In the examples below, each
group is attached to the main chain at the left end.

The divalent aliphatic group preferably has a chain structure to a ring
structure, more preferably has a straight-chain structure to a branched
chain structure. The divalent aliphatic group preferably contains 1 to
20, more preferably 1 to 15, even more preferably 1 to 12, still more
preferably 1 to 10, most preferably 1 to 8 carbon atoms. Examples of
substituents on the divalent aliphatic group include halogen atoms (F,
Cl, Br, I), hydroxy, carboxy, amino, cyano, aryl, alkoxy, aryloxy, acyl,
acyloxy, monoalkylamino, dialkylamino, arylamino and diarylamino and the
like.

[0097] The divalent aromatic group refers to a divalent monocyclic or
polycyclic aromatic hydrocarbon group. Specific examples of the divalent
aromatic group include, for example, 1,2-phenylene, 1,3-phenylene,
1,4-phenylene, biphenyl-4,4'-diyl, diphenylmethane-4,4'-diyl,
3,3'-dimethylbiphenyl-4,4'-diyl, 1,2-naphthalene, 1,5-naphthalene,
2,6-naphthalene and the like. Examples of substituents on the divalent
aromatic group include the examples of substituents on the divalent
aliphatic group listed above, as well as alkyl.

[0098] Preferably, Y21 to Y26 represent a single bond, a
divalent aromatic group, L1, L2, L3 and L4, more preferably a single
bond, L1 and L2.

[0099] M1 to M8 each independently represent a hydrogen atom, a
metal atom contained in an alkali metal or an alkaline earth metal or
ammonium, preferably a hydrogen atom, or a metal atom contained in an
alkaline metal, more preferably a hydrogen atom.

[0100] Among the structures represented by formulae (a2-1) to (a2-6)
above, the structure interacting with the substrate surface is preferably
a structure represented by formulae (a2-1), (a2-2) and (a2-6) above, more
preferably a structure represented by formula (a2-1) or (a2-2) above to
improve staining resistance and printing durability. Further, M1 and
M2, and M3 and M4 are preferably a hydrogen atom,
respectively in both of the structure represented by formula (a2-1) above
and the structure represented by formula (a2-2) above.

Further, the functional group interacting with the substrate surface is
preferably the carboxylic acid-containing group, sulfonic acid,
phosphoric acid ester or a salt thereof, phosphonic acid or a salt
thereof to improve staining resistance and printing durability.

[0101] Specifically, the structures represented by formulae (a2-1) to
(a2-6) above include the structures shown below, but the present
invention is not limited to the specific examples below. In the formulae
below, the asterisk (*) indicates the point of attachment to the main
chain of the polymer compound.

##STR00035##

[0102] The repeating unit (a2) having at least one structure interacting
with the substrate surface is preferably a repeating unit represented by
formula (A2) below.

##STR00036##

[0103] In formula (A2) above, Ra' to Rc' each independently
represent a hydrogen atom, C1-6 alkyl or halogen atom. L4 represents
a single bond or a divalent linking group. (a2) represents a structure
represented by formulae (a2-1) to (a2-6) above, and it is attached to a
carbon atom at the point indicated by the asterisk (*) in formulae (a2-1)
to (a2-6).

[0104] In the copolymer (A), the proportion of the repeating unit having a
structure represented by formulae (a2-1) to (a2-6) (a2) above is
preferably in the range of 1 to 99 mol %, more preferably in the range of
1 to 90 mol %, even more preferably in the range of 1 to 80 mol % based
on the total repeating units to improve staining resistance and
developability.

[0105] (a3) Repeating unit having a hydrophilic group in a side chain:

The copolymer (A) preferably comprises (a3) a repeating unit having at
least one hydrophilic group in a side chain to confer high hydrophilicity
on the substrate surface of non-image areas. The hydrophilic group is
selected from monovalent or divalent or polyvalent hydrophilic groups
capable of readily forming a hydrogen bond/van der Waals bond/ionic bond
with a water molecule, specifically including hydroxy, carboxyl, amino,
sulfo, positively or negatively charged groups, zwitterionic groups and
metal salts thereof and the like. Among them, hydroxy, sulfonic acid,
alkyleneoxy such as ethyleneoxy and propyleneoxy, quaternary ammonium,
amide, ether bond-containing groups, or salts obtained by neutralizing
acid groups such as carboxylic acid, sulfonic acid, phosphoric acid and
the like, heterocyclic groups containing positively charged nitrogen
atoms and the like are preferred, for example. These hydrophilic groups
may also be used as the repeating unit (a2) having a structure
interacting with the substrate surface in a side chain.

[0106] In the present invention, the repeating unit (a3) having a
hydrophilic group in a side chain is especially preferably a repeating
unit having a zwitterionic structure in a side chain to confer high
hydrophilicity on the substrate surface of non-image areas.

In the lithographic printing plate precursor of the present invention,
the hydrophilic group contained in the copolymer (A) is especially
preferably selected from zwitterionic structures represented by formula
(a3-1) or (a3-2) below:

##STR00037##

[0107] In formula (a3-1) above, R31 and R32 each independently
represent a hydrogen atom, alkyl, alkenyl, alkynyl, aryl, or
heterocyclyl, or R31 and R32 may be joined together to form a
ring structure, L31 represents a linking group, and A- represents an
anion-containing structure. Y3 represents a divalent linking group
attached to the main chain of the polymer compound. The asterisk (*)
indicates the point of attachment to the main chain of the polymer
compound.

[0108] The ring structure formed by R31 and R32 together is
preferably a 5- to 10-membered ring, more preferably a 5- or 6-membered
ring, and may contain a heteroatom such as oxygen atom or the like.

[0110] Examples of alkyls represented by R31 and R32 include
methyl, ethyl, propyl, octyl, isopropyl, t-butyl, isopentyl,
2-ethylhexyl, 2-methylhexyl, cyclopentyl and the like. Examples of
alkenyls represented by R31 and R32 include vinyl, allyl,
prenyl, geranyl, oleyl and the like.

Examples of alkynyls represented by R31 and R32 include
ethynyl, propargyl, trimethylsilylethynyl and the like. Further, examples
of aryls represented by R31 and R32 include phenyl, 1-naphthyl,
2-naphthyl and the like. Further, examples of heterocyclyls include
furanyl, thiophenyl, pyridinyl and the like.

[0112] Especially preferred examples of R31 and R32 include a
hydrogen atom, methyl, or ethyl because of the resulting effect and
availability.

[0113] The divalent linking group represented by Y3 is a single bond
or a divalent linking group selected from the group consisting of --CO--,
--O--, --NH--, a divalent aliphatic group, a divalent aromatic group and
a combination thereof.

[0114] Specific examples of Y3 consisting of the combination
described above are shown below. In the examples below, each group is
attached to the main chain at the left end.

[0115] The divalent aliphatic group and the divalent aromatic group
described above refer to include the linking groups mentioned as examples
of the divalent aliphatic group containing 1 to 14 carbon atoms for
Z1, and the linking groups mentioned as examples of the divalent
aromatic group containing 6 to 14 carbon atoms for L1, respectively.
Examples of substituents on the divalent aliphatic group and the divalent
aromatic group include the substituents with which the groups represented
by R31 and R32 may be further substituted.

[0116] Among others, Y3 is preferably a single bond, --CO--, a
divalent aliphatic group, a divalent aromatic group, or L101 to L104
shown above. Further, Y1 is preferably L101 or L103 shown
above, more preferably L103 to improve staining resistance. Further, the
divalent aliphatic group of L103 is preferably a straight-chain alkylene
containing 2 to 4 carbon atoms, most preferably a straight-chain alkylene
containing 3 carbon atoms for convenience of synthesis.

L31 represents a linking group, preferably a linking group selected
from the group consisting of --CO--, --O--, --NH--, a divalent aliphatic
group, a divalent aromatic group and a combination thereof, and
preferably contains 30 or less carbon atoms including carbon atoms of the
optionally present substituents described below. Specific examples
thereof include alkylene (preferably containing 1 to 20 carbon atoms,
more preferably 1 to 10 carbon atoms), and arylene (preferably containing
5 to 15 carbon atoms, more preferably 6 to 10 carbon atoms) such as
phenylene, xylylene and the like. Among others, L31 is preferably a
straight-chain alkylene containing 3 to 5 carbon atoms, more preferably a
straight-chain alkylene containing 4 or 5 carbon atoms, most preferably a
straight-chain alkylene containing 4 carbon atoms to improve staining
resistance. Specific examples of L31 include, for example, the
following linking groups:

[0119] To improve staining resistance, A.sup.- is most preferably
sulfonate. Further, a preferred combination of L31 and A.sup.- in
formula (a1-1) above is a combination of a straight-chain alkylene
containing 4 or 5 carbon atoms and sulfonate, most preferably a
combination of a straight-chain alkylene containing 4 carbon atoms and
sulfonate.

[0120] In a preferred combination, Y3 is L101 or L103 shown above,
R31 and R32 are ethyl or methyl, L31 is a straight-chain
alkylene containing 4 or 5 carbon atoms, and A.sup.- is sulfonate. In a
more preferred combination, Y3 is L103 shown above, R31
and R32 are methyl, L31 is a straight-chain alkylene containing
4 carbon atoms, and A.sup.- is sulfonate. The zwitterionic structure
represented by formula (a3-1) above specifically includes the structures
shown below. In the formulae below, the asterisk (*) indicates the point
of attachment to the main chain of the copolymer (A).

In formula (a3-2), L32 represents a divalent linking group, and
E.sup.+ represents a cation-containing structure. Y4 represents a
single bond, or a divalent linking group selected from the group
consisting of --CO--, --O--, --NH--, a divalent aliphatic group, a
divalent aromatic group and a combination thereof. The asterisk (*)
indicates the point of attachment to the main chain of the copolymer.

[0122] Also in formula (a3-2) above, L32 represents a linking group
preferably selected from the group consisting of --CO--, --O--, --NH--, a
divalent aliphatic group, a divalent aromatic group and a combination
thereof. Specific examples and preferred examples thereof are the same as
mentioned above for the linking group represented by L31. Y4
has the same meaning as defined for Y3 in formula (a3-2) above, and
also covers similar preferred examples. E.sup.+ represents a
cation-containing structure, preferably a structure containing ammonium,
phosphonium, iodonium, or sulfonium, more preferably a structure
containing ammonium or phosphonium, especially preferably a structure
containing ammonium. Examples of cation-containing structures include
trimethylammonio, triethylammonio, tributylammonio,
benzyldimethylammonio, diethylhexylammonio,
(2-hydroxyethyl)dimethylammonio, pyridinio, N-methylimidazolio,
N-acridinio, trimethylphosphonio, triethylphosphonio, triphenylphosphonio
and the like.

In a most preferred combination of L32, Y4 and E.sup.+,
L32 is an alkylene containing 2 to 4 carbon atoms, Y4 is L101
or L103 shown above, and E.sup.+ is trimethylammonio or triethylammonio.
The zwitterionic structure represented by formula (a3-2) specifically
includes the structures shown below. In the formulae below, the asterisk
(*) indicates the point of attachment to the main chain of the copolymer
(A).

##STR00042##

[0123] In the present invention, the repeating unit having a zwitterionic
structure is preferably represented by (A3) specifically.

##STR00043##

wherein R201 to R203 each independently represent a hydrogen
atom, C1-6 alkyl or halogen atom. G represents a divalent linking group
having a hydrophilic group, or a structure represented by formula (a3-1)
or (a3-2), and is attached to a carbon atom at the point indicated by the
asterisk (*) in formulae (a3-1) to (a3-2).

[0124] In formula (A3) above, the side chain G is especially preferably a
structure represented by formula (a3-1).

[0125] In the present invention, the proportion of the repeating unit (a3)
having a hydrophilic group in a side chain based on the total repeating
units constituting the copolymer (A) is preferably in the range of 1 to
70 mol %, more preferably in the range of 1 to 50 mol %, even more
preferably in the range of 1 to 30 mol % based on the total repeating
units to improve staining resistance and developability.

[0126] Extra repeating unit:

Further, the copolymer (A) may comprise an extra repeating unit other
than the repeating units described above (hereinafter also referred to as
an "extra repeating unit") as a component of a copolymer. Extra repeating
units that may be contained as such repeating units include repeating
units derived from various known monomers. Preferred examples include
repeating units derived from known monomers such as acrylic acid esters,
methacrylic acid esters, acrylamides, methacrylamides, vinyl esters,
styrenes, acrylic acid, methacrylic acid, acrylonitrile, maleic
anhydride, maleimide and the like. Various properties of the layers such
as film-forming properties, film strength, hydrophilicity,
hydrophobicity, solubility, reactivity, stability and the like can be
improved or controlled as appropriate by introducing the extra repeating
unit into the copolymer (A). Among others, monomers selected from acrylic
acid esters, methacrylic acid esters, N,N-2-substituted acrylamides,
N,N-2-substituted methacrylamides, styrenes, acrylonitriles,
methacrylonitriles and the like are included.

[0128] In the copolymer (A), the proportion of the extra repeating unit is
preferably 0 to 60 mol %, more preferably 0 to 40 mol %, even more
preferably 0 to 30%.

[0129] <<Copolymers of the Present Invention>>

Among the copolymers (A) that can be used in these lithographic printing
plate precursors of the present invention, copolymers of the present
invention are polymer compounds having the characteristic structure as
follows. The copolymers of the present invention are characterized in
that they comprise: (a1) a repeating unit having a structure represented
by formula (a1-1) below in a side chain; (a2) a repeating unit having at
least one of the structures represented by formulae (a2-1), (a2-1),
(a2-3), (a2-4), (a2-5) and (a2-6) in a side chain; and (a3') a repeating
unit having a zwitterionic structure represented by formula (a3-1) or
(a3-2) below in a side chain.

##STR00044##

In formula (a1-1), L1 represents a single bond, a divalent aromatic
group containing 6 to 14 carbon atoms, --C(═O)--O--, or
--C(═O)--NR2-- (wherein R2 represents a hydrogen atom,
alkyl or aryl). Z1 represents a divalent linking group selected from
the group consisting of a divalent aliphatic group containing 1 to 14
carbon atoms, a divalent aromatic group containing 6 to 14 carbon atoms,
--NH--, --O--, --S-- and a combination thereof, provided that both ends
are not --NH--, --O-- or --S--, and when L1 is a divalent aromatic
group containing 6 to 14 carbon atoms, Z1 is not a divalent aromatic
group containing 6 to 14 carbon atoms, and the divalent aliphatic group,
divalent aromatic group and --NH-- may have a substituent instead of a
hydrogen atom. R1 represents a hydrogen atom, alkyl, aryl,
heterocyclyl, sulfo, alkylsulfonyl and arylsulfonyl. R1 represents a
hydrogen atom, alkyl, aryl, heterocyclyl, sulfo, alkylsulfonyl and
arylsulfonyl. R21, R22 and R23 each independently
represent a hydrogen atom, halogen atom or C1-8 alkyl. The asterisk (*)
indicates the point of attachment to the main chain of the copolymer.

##STR00045##

wherein M1 to M8 each independently represent a hydrogen atom,
a metal atom contained in an alkali metal or an alkaline earth metal or
ammonium. R41 to R46 each independently represent a hydrogen
atom or alkyl. Y21 to Y26 represent a single bond, or a
divalent linking group selected from the group consisting of --CO--,
--O--, --NH--, a divalent aliphatic group, a divalent aromatic group and
a combination thereof. The asterisk (*) indicates the point of attachment
to the main chain of the polymer compound.

##STR00046##

In formula (a3-1), R31 and R32 each independently represent a
hydrogen atom, alkyl, alkenyl, alkynyl, aryl, or heterocyclyl, or
R31 and R32 may be joined together to form a ring structure,
L31 represents a linking group, and A- represents an
anion-containing structure. Y3 represents a single bond, or a
divalent linking group selected from the group consisting of, --CO--,
--O--, --NH--, a divalent aliphatic group, a divalent aromatic group and
a combination thereof. The asterisk (*) indicates the point of attachment
to the main chain of the polymer compound.

##STR00047##

In formula (a3-2) above, L32 represents a linking group, and E+
represents a cation-containing structure. Y4 represents a single
bond, or a divalent linking group selected from the group consisting of
--CO--, --O--, --NH--, a divalent aliphatic group, a divalent aromatic
group and a combination thereof. The asterisk (*) indicates the point of
attachment to the main chain of the polymer compound.

[0130] (Weight Average Molecular Weight)

The weight average molecular weight (Mw) of the copolymer (A) can be
appropriately selected depending on the performance design of the
lithographic printing plate precursor. To improve printing durability and
staining resistance, the weight average molecular weight is preferably
2,000 to 1,000,000, more preferably 2,000 to 500,000, most preferably
8,000 to 300,000.

[0131] Specific examples of the copolymer (A) are shown below along with
their weight average molecular weights, but the present invention is not
limited to these examples. It should be noted that the composition ratio
of the polymer structures are expressed in mass percentage.

[0132] <<Processes for Preparing the Copolymers of the Present
Invention>>

The specific polymer compounds (copolymers (A)) and, among others, the
copolymers of the present invention having a characteristic structure can
be synthesized by known methods, but preferably by using radical
polymerization followed by ureation reaction using the amino group in a
polymer side chain and an isocyanate having a radically polymerizable
reactive group.

[0133] Typical techniques for radical polymerization are described in, for
example, "New Polymer Experimental Chemistry, vol. 3" (Edited by the
Society of Polymer Science, Japan, published by KYORITSU SHUPPAN CO.,
LTD., Mar. 28, 1996); "Synthesis and Reaction of Polymers, vol. 1"
(Edited by the Society of Polymer Science, Japan, published by KYORITSU
SHUPPAN CO., LTD., May 1992); "New Textbook of Experimental Chemistry,
vol. 19, Polymer Chemistry (I) (Edited by the Chemical Society of Japan,
published by Maruzen Company, Limited, Nov. 20, 1980); "Textbook of
Material Engineering, Polymer Synthetic Chemistry" (published by Tokyo
Denki University Press, September 1995) and the like, and these
techniques can be applied.

[0134] The processes for preparing the copolymers of the present invention
are characterized by preparing a unit having a structure represented by
formula (a1-1) above by using the reactive reagents. Details are as
described for the generation of the unit having a structure represented
by formula (a1-1) above.

Thus, the processes for preparing the copolymers of the present invention
are characterized in that they comprise introducing (a1) the repeating
unit having a structure represented by formula (a1-1) above in a side
chain by reacting a polymer comprising: (a0) a repeating unit having a
structure represented by formula (a1-0) below in a side chain; (a2) the
repeating unit having a structures represented by any one of formulae
(a2-1), (a2-1), (a2-3), (a2-4), (a2-5) and (a2-6) above in a side chain;
and (a3') the repeating unit having a zwitterionic structure represented
by formula (a3-1) or (a3-2) above in a side chain; with a compound
represented by formula (b-1) or (b-2) below.

##STR00066##

In formula (a1-0), L101 represents a single bond, a divalent
aromatic group containing 6 to 14 carbon atoms, --C(═O)--O--, or
--C(═O)--NR102-- (wherein R102 represents a hydrogen atom,
alkyl or aryl). Z101 represents a divalent linking group selected
from the group consisting of a divalent aliphatic group containing 1 to
14 carbon atoms, a divalent aromatic group containing 6 to 14 carbon
atoms, --NH--, --O--, --S-- and a combination thereof, provided that both
ends are not --NH--, --O-- or --S--, and when L1 is a divalent
aromatic group containing 6 to 14 carbon atoms, Z1 is not a divalent
aromatic group containing 6 to 14 carbon atoms, and the divalent
aliphatic group, divalent aromatic group and --NH-- may have a
substituent instead of a hydrogen atom. R101 represents a hydrogen
atom, alkyl, aryl, heterocyclyl, sulfo, alkylsulfonyl and arylsulfonyl.
The asterisk (*) indicates the point of attachment to the main chain of
the copolymer.

[0135] In formula (a1-0) above, preferred ranges of L101, R102,
Z101, and R101 are similar to the preferred ranges of L1,
R1, Z1, and R2 in formula (a1-1) above.

[0136] (B) Polymerization Initiator

The photosensitive layer of the present invention preferably contains a
polymerization initiator (hereinafter also referred to as an "initiator
compound"). In the present invention, a radical polymerization initiator
is preferably used.

[0137] The initiator compound may be arbitrarily selected from compounds
known among those skilled in the art without limitation. Specific
examples include trihalomethyl compound, carbonyl compound, organic
peroxide, azo compound, azide compound, metallocene compound,
hexaarylbiimidazole compound, organic boron compound, disulfone compound,
oxim ester compound, onium salt, and iron arene complex. In particular,
the initiator compound is preferably at least one species selected from
the group consisting of hexaarylbiimidazole compound, onium salt,
trihalomethyl compound and metallocene compound, and is particularly
hexaarylbiimidazole compound, or onium salt. Two or more species of them
may be used in combination as the polymerization initiator.

[0138] The hexaarylbiimidazole compound is exemplified by lophine dimers
described in European Patent Nos. 24,629 and No. 107,792, and U.S. Pat.
No. 4,410,621, which are exemplified by
2,2'-bis(o-chlorophenyl)-4,4',5,5'-tetraphenylbiimidazole,
2,2'-bis(o-bromophenyl)-4,4',5,5'-tetraphenylbiimidazole,
2,2'-bis(o,p-dichlorophenyl)-4,4',5,5'-tetraphenylbiimidazole,
2,2'-bis(o-chlorophenyl)-4,4',5,5'-tetra(m-methoxyphenyl)biimidazole,
2,2'-bis(o,o'-dichlorophenyl)-4,4',5,5'-tetraphenylbiimidazole,
2,2'-bis(o-nitrophenyl)-4,4',5,5'-tetraphenylbiimidazole,
2,2'-bis(o-methylphenyl)-4,4',5,5'-tetraphenylbiimidazole, and
2,2'-bis(o-trifluoromethylphenyl)-4,4',5,5'-tetraphenyl biimidazole. It
is particularly preferable that the hexaarylbiimidazole compound is used
in combination with a sensitizing dye which shows maximum absorption in
the wavelength range from 300 to 450 nm.

[0147] The polymerization initiator is preferably used alone, or in
combination of two or more species.

[0148] The content of the polymerization initiator in the photosensitive
layer is preferably 0.01 to 20% by mass relative to the total solid
content of the image recording layer, more preferably 0.1 to 15% by mass,
and still more preferably 1.0 to 10% by mass.

[0149] (C) Polymerizable Compound

[0150] The polymerizable compound used for the image recording layer is an
addition polymerizable compound having at least one ethylenic unsaturated
double bond, and is selected from compounds having at least one, and
preferably two, terminal ethylenic unsaturated bonds. These compounds
typically have any of chemical forms including monomer; prepolymer such
as dimer, trimer and oligomer; and mixtures of them. Examples of the
monomer include unsaturated carboxylic acid (for example, acrylic acid,
methacrylic acid, itaconic acid, crotonic acid, isocrotonic acid, maleic
acid), esters of them, and amides of them. More preferable examples
include esters formed between unsaturated carboxylic acid and polyhydric
alcohol compound, and amides formed between unsaturated carboxylic acid
and polyvalent amine compound. Still other preferable examples include
adducts of unsaturated carboxylate esters or amides having nucleophilic
substituent group such as hydroxy group, amino group, mercapto group or
the like, formed together with monofunctional or polyfunctional
isocyanates or epoxys; and dehydration condensation product formed
together with monofunctional or polyfunctional carboxylic acid. Still
other preferable examples include adducts of unsaturated carboxylate
esters or amides having electrophilic substituent group such as
isocyanate group and epoxy group, formed together with monofunctional or
polyfunctional alcohols, amines, or thiols; and substitution products of
unsaturated carboxylate esters or amides having eliminative substituent
group such as halogen group and tosyloxy group, formed together with
monofunctional or polyfunctional alcohols, amines, or thiols.

[0151] Also compounds obtained by replacing the above-described
unsaturated carboxylic acid with unsaturated phosphonic acid, styrene,
vinyl ether or the like are also adoptable. These compounds are disclosed
in Published Japanese Translation of PCT International Publication for
Patent Application No. 2006-508380, Japanese Laid-Open Patent Publication
Nos. 2002-287344, 2008-256850, 2001-342222, H09-179296, H09-179297,
H09-179298, 2004-294935, 2006-243493, 2002-275129, 2003-64130,
2003-280187, and H10-333321.

[0153] Also urethane-based addition polymerizable compound, obtainable by
addition polymerization between the isocyanate and hydroxy group, is
preferable. Preferable examples of this sort of compound include vinyl
urethane compound having two or more polymerizable vinyl groups per one
molecule, which is obtainable by addition reaction between a vinyl
monomer having a hydroxy group represented by the formula (P) below, and
a polyisocyanate compound having two or more isocyanate groups per one
molecule, as described in Examined Japanese Patent Publication No.
S48-41708.

[0155] Among them, for the lithographic printing plate precursor adapted
to the on-machine development, isocyanurate of ethylene oxide-modified
acrylate such as tris(acryloyloxyethyl)isocyanurate, and
bis(acryloyloxyethyl)hydroxyethyl isocyanurate are particularly
preferable, from the viewpoint of good balance between hydrophilicity
contributive to the on-press developability and polymerizability
contributive to the printing durability.

[0156] Structure of the polymerizable compound (C), and method of use,
including whether it is used alone or in combination with other species,
or amount of use, may be arbitrarily determined depending on a final
desired goal of performance design of lithographic printing plate
precursor. The content of the polymerizable compound (C) is preferably 5
to 75% by mass of the total solid content of the image recording layer,
more preferably 25 to 70% by mass, and particularly 30 to 60% by mass.

[0157] (D) Binder

[0158] The binder (D) contained in the photosensitive layer of the
lithographic printing plate precursor according to the present invention
is selected from those capable of keeping the photosensitive layer
component on the support, and removable by the developer. Examples of the
binder (E) include (meth)acrylic polymer, polyurethane resin, polyvinyl
alcohol resin, polyvinyl butyral resin, polyvinyl formal resin, polyamide
resin, polyester resin, and epoxy resin. In particular, (meth)acrylic
polymer, polyurethane resin, and polyvinyl butyral resin are preferably
used. More preferable examples include (meth)acrylic polymer,
polyurethane resin, and polyvinyl butyral resin.

[0159] In the present invention, "(meth)acrylic polymer" means copolymer
having, as a polymerizable component, (meth)acrylic acid derivative such
as (meth)acrylic acid, (meth)acryliate ester (alkyl ester, aryl ester,
allylester, etc.), (meth)acrylamide and (meth)acrylamide derivative.
"Polyurethane resin" means polymer produced by condensation reaction
between a compound having two or more isocyanate groups and a compound
having two or more hydroxy groups. "Polyvinyl butyral resin" means
polymer synthesized by allowing polyvinyl alcohol obtained by partially
or totally saponifying polyvinyl acetate to react with butyl aldehyde
under an acidic condition (acetal forming reaction), which also includes
polymer having introduced therein acid group and so forth, obtained by
allowing the residual hydroxy group to react with a compound having acid
group.

[0160] One preferable example of the (meth)acrylic polymer is a copolymer
having a repeating unit which contains an acid group. The acid group is
exemplified by carboxylate group, sulfonate group, phosphonate group,
phosphate group, and sulfonamide group, wherein carboxylate group is
particularly preferable. The repeating unit having acid group preferably
used herein includes a repeating unit derived from (meth)acrylic acid, or
a unit represented by the formula (I) below:

##STR00068##

[0161] In the formula (I), R211 represents a hydrogen atom or methyl
group, R212 represents a single bond or n211 monovalent linking
groups. A211 represents an oxygen atom or --NR213--, and
R213 represents a hydrogen atom or C1-10 monovalent hydrocarbon
group. n211 represents an integer from 1 to 5.

[0162] The linking group represented by R212 in the formula (I) is
composed of hydrogen atom, carbon atom, oxygen atom, nitrogen atom,
sulfur atom and halogen atom, with a total number of atoms of preferably
1 to 80. More specifically, the alkylene group, substituted alkylene
group, arylene group, and substituted arylene group are exemplified. A
plurality of these divalent groups may be linked with any of amide bond,
ether bond, urethane bond, urea bond and ester bond. R212 preferably
has a structure in which a plurality of single bonds, alkylene groups,
substituted alkylene groups and alkylene groups and/or substituted
alkylene groups are linked with any of amide bond, ether bond, urethane
bond, urea bond, and ester bond; more preferably has a structure in which
a plurality of single bonds, C1-5 alkylene groups, C1-5
substituted alkylene groups and C1-5 alkylene groups and/or
C1-5 substituted alkylene groups are linked with any of amide bond,
ether bond, urethane bond, urea bond, and ester bond; and particularly
has a structure in which a plurality of single bonds, C1-3 alkylene
group, C1-3 substituted alkylene group, and C1-3 alkylene group
and/or C1-3 substituted alkylene groups are linked with any of amide
bond, ether bond, urethane bond, urea bond, and ester bond.

[0164] R213 is preferably a hydrogen atom or C1-5 hydrocarbon
group, more preferably a hydrogen atom or C1-3 hydrocarbon group,
and particularly a hydrogen atom or methyl group.

[0165] n211 is preferably 1 to 3, more preferably 1 or 2, and
particularly 1.

[0166] Ratio of the content (mol %) of the polymerizable component having
carboxylate group, relative to the total polymerizable components of the
(meth)acrylic polymer is preferably 1 to 70% from the viewpoint of
developability, more preferably 1 to 50% considering a good balance
between the developability and printing durability, and particularly 1 to
30%.

[0167] It is preferable for the (meth)acrylic polymer used in the present
invention to additionally have a crosslinkable group. The crosslinkable
group herein means a group capable of crosslinking the binder (D), in the
process of radical polymerization reaction which proceeds in the
photosensitive layer, when the lithographic printing plate precursor is
exposed to light. While the functional group is not specifically limited
so long as it can exhibit the above-described function, examples of the
functional group capable of proceeding addition polymerization reaction
include ethylenic unsaturated binding group, amino group, and epoxy
group. The functional group may also be a functional group capable of
producing a radical upon being exposed to light, and this sort of
crosslinkable group is exemplified by thiol group and halogen group.
Among them, ethylenic unsaturated binding group is preferable. The
ethylenic unsaturated binding group is preferably styryl group,
(meth)acryloyl group, or allyl group.

[0168] The binder (D) cures in such a way that a free radical
(polymerization initiating radical, or propagating radical in the process
of polymerization of radical or polymerizable compound) attaches to the
crosslinkable functional group, and crosslinkage is formed among the
polymer molecules thereof, by addition polymerization which proceeds
directly among the polymer molecules or by sequential polymerization of
the polymerizable compounds. Alternatively, the binder cures in such a
way that atoms (for example, hydrogen atoms on carbon atoms adjacent to
the functional crosslinking groups) in the polymer are abstracted by free
radicals to produce polymer radicals, and the resultant polymer radicals
then combine with each other to produce the crosslinkages among the
polymer molecules.

[0169] The content of the crosslinkable group in the (meth)acrylic polymer
(content of radical polymerizable unsaturated double bond determined by
iodometry) is preferably 0.01 to 10.0 mmol per one gram of the binder
(D), more preferably 0.05 to 9.0 mmol, and particularly 0.1 to 8.0 mmol.

[0170] Besides the above-described repeating unit having an acid group,
and the polymerization unit having a crosslinkable group, the
(meth)acrylic polymer used in the present invention may have a
polymerization unit of alkyl (meth)acrylate or aralkyl (meth)acrylate,
polymerization unit of (meth)acrylamide or its derivative, polymerization
unit of α-hydroxymethyl acrylate, or polymerization unit of styrene
derivative. The alkyl group of alkyl (meth)acrylate is preferably a
C1-5 alkyl group, or an alkyl group having the above-described
C2-8 substituent group, and more preferably methyl group. The
aralkyl (meth)acrylate is exemplified by benzyl (meth)acrylate. The
(meth)acrylamide derivative is exemplified by N-isopropylacrylamide,
N-phenylmethacrylamide, N-(4-methoxycarbonylphenyl)methacrylamide,
N,N-dimethylacrylamide, and morpholinoacrylamide. The
α-Hydroxymethyl acrylate is exemplified by ethyl
α-hydroxymethyl acrylate, and cyclohexyl α-hydroxymethyl
acrylate. The styrene derivative is exemplified by styrene, and
4-tert-butylstyrene.

[0171] For the case where the lithographic printing plate precursor is
intended for on-machine development, the binder (D) preferably has a
hydrophilic group. The hydrophilic group contributes to impart on-press
developability to the photo sensitive layer. In particular, by allowing
the crosslinkable group and the hydrophilic group to coexist, the
printing durability and the on-press developability may be compatible.

[0172] Examples of the hydrophilic group possibly bound to the binder (D)
include hydroxy group, carboxyl group, alkylene oxide structure, amino
group, ammonium group, amide group, sulfo group, and phosphate group.
Among them, the alkylene oxide structure having 1 to 9 C2-3alkylene
oxide units is preferable. The hydrophilic group may be introduced into
the binder, typically by allowing monomers having hydrophilic group to
copolymerize.

[0173] Preferable examples of the polyurethane resin include those
described in paragraphs

[0107]
of Japanese Laid-Open Patent Publication No. 2005-250438, and paragraphs

[0021] to

[0083] of Japanese Laid-Open Patent Publication No.
2005-250158.

[0174] Preferable examples of the polyvinyl butyral resin include those
described in paragraphs

[0006] to

[0013] of Japanese Laid-Open Patent
Publication No. 2001-75279.

[0175] The binder (D) may be neutralized by a basic compound at a part of
the acid groups. The basic compound is exemplified by compounds having
basic nitrogen atom, alkali metal hydroxide, and quaternary ammonium salt
of alkali metal.

[0176] The binder (D) preferably has a mass average molecular weight of
5,000 or larger, more preferably 10,000 to 300,000, and preferably has a
number average molecular weight of 1,000 or larger, and more preferably
2000 to 250,000. The polydispersibility (mass average molecular
weight/number average molecular weight) is preferably 1.1 to 10.

[0177] The binder (D) may be used alone or in combination of two or more
species.

[0178] The content of the binder (D) is preferably 5 to 75% by mass of the
total solid content of the photo sensitive layer, from the viewpoint of
satisfactory levels of strength in the image-forming area and image
formability, and more preferably 10 to 70% by mass, and still more
preferably 10 to 60% by mass.

[0179] Total content of the polymerizable compound (C) and the binder (D)
relative to the total solid content of the photo sensitive layer is
preferably 90% by mass or less. The content exceeding 90% by mass may
result in degraded sensitivity and developability. The content is more
preferably 35 to 80% by mass.

(E) Sensitizing Dye

[0180] The photo sensitive layer preferably contains a dye. The dye is
preferably a sensitizing dye(E).

[0181] The sensitizing dye used for the image recording layer of the
lithographic printing plate precursor according to the present invention
may be arbitrarily selected without special limitation, so long as it can
go into an excited state upon absorption of light in the process of
pattern-wise exposure, and can supply energy to the polymerization
initiator typically by electron transfer, energy transfer or heat
generation, so as to improve the polymerization initiating property. In
particular, sensitizing dyes showing maximum absorption in the wavelength
range from 350 to 450 nm are preferably used.

[0183] Among the sensitizing dyes showing maximum absorption in the
wavelength range from 350 to 450 nm, preferable dyes are those
represented by the formula (IX), from the viewpoint of large sensitivity.

##STR00069##

[0184] In the formula (IX), A221 represents an aryl group or
heteroaryl group which may have a substituent group, and X221
represents an oxygen atom, sulfur atom or ═N(R223). Each of
R221, R222 and R223 independently represents a monovalent
group of non-metallic atom, wherein A221 and R221, or R222
and R223, may combine respectively to form an aliphatic or aromatic
ring.

[0185] The formula (IX) will now be further detailed. The monovalent group
of non-metallic atom represented by R221, R222 or R223 is
preferably a hydrogen atom, substituted or unsubstituted alkyl group,
substituted or unsubstituted alkenyl group, substituted or unsubstituted
aryl group, substituted or unsubstituted heteroaryl group, substituted or
unsubstituted alkoxy group, substituted or unsubstituted alkylthio group,
hydroxy group, and halogen atom.

[0186] The aryl group and heteroaryl group represented by A221, which
may have a substituent group, are same as the substituted or
unsubstituted aryl group, and substituted or unsubstituted heteroaryl
group represented respectively by R221, R222 and R223.

[0187] Specific examples of the sensitizing dye preferably used herein
include the compounds described in paragraphs

[0189] Next, the sensitizing dye showing maximum absorption in the
wavelength range from 750 to 1400 nm (also referred to as "infrared
absorber", hereinafter) will be described. The infrared absorber
preferably used herein is dye or pigment.

[0192] In the formula (a), X131 represents a hydrogen atom, halogen
atom, --NPh2, --X132-L131 or the group shown below, where

##STR00071##

[0193] In the formula, X132 represents an oxygen atom, nitrogen atom
or sulfur atom, and L131 represents a C1-12 hydrocarbon group,
aryl group having a hetero atom (N, S, O, halogen, Se), and C1-12
hydrocarbon group having a hetero atom. Xa.sup.- is synonymous with
Za.sup.- described later. R141 represents a substituent group
selected from hydrogen atom or alkyl group, aryl group, substituted or
unsubstituted amino group, and halogen atom.

[0194] Each of R131 and R132 independently represents C1-12
hydrocarbon group. From the viewpoint of stability of coating liquid for
forming the photo sensitive layer, each of R131 and R132 is
preferably a C2 or longer hydrocarbon group. R131 and R132
may combine with each other to form a ring which is preferably a
five-membered ring or six-membered ring.

[0195] Ar131 and Ar132 may be same or different, and each
represents an aryl group which may have a substituent group. Preferable
examples of the aryl group include benzene ring group and naphthalene
ring group. Preferable examples of the substituent group include C12
or shorter hydrocarbon group, halogen atom, and C12 or shorter alkoxy
group. Y131 and Y132 may be same or different, and each
represents a sulfur atom or C12 or shorter dialkylmethylene group.
R133 and R134 may be same or different, and each represents a
C20 or shorter hydrocarbon group which may have a substituent group.
Preferable examples of the substituent group include a C12 or
shorter alkoxy group, carboxyl group, and sulfo group. R135,
R136, R137 and R138 may be same or different, and each
represents a hydrogen atom or C12 or shorter hydrocarbon group. From
the viewpoint of availability of the source materials, hydrogen atom is
preferable. Za.sup.- represents a counter anion. Note that
Za.sup.- is not necessary if the cyanine colorant represented by the
formula (a) has an anionic substituent group in the structure thereof,
and is omissible if there is no need of neutralization of electric
charge. Preferable examples of Za.sup.- include halide ion,
perchlorate ion, tetrafluoroborate ion, hexafluorophosphate ion and
sulfonate ion from the viewpoint of storage stability of coating liquid
for forming the photo sensitive layer. Particularly preferable examples
include perchlorate ion, hexafluorophosphate ion and aryl sulfonate ion.

[0196] Specific examples of the cyanine colorant represented by the
formula (a) include the compounds described in paragraphs

[0198] The infrared absorbing dye may be used alone, or in combination of
two or more species, and may contain an infrared absorber other than
infrared absorbing dye, which is exemplified by pigment. As the pigment,
the compounds described in paragraphs

[0072] to

[0076] of Japanese
Laid-Open Patent Publication No. 2008-195018 are preferable.

[0199] The content of the sensitizing dye (E) is preferably 0.05 to 30
parts by mass relative to the total solid content (100 parts by mass) of
the photo sensitive layer, more preferably 0.1 to 20 parts by mass, and
particularly 0.2 to 10 parts by mass.

[0200] (F) Low-Molecular-Weight Hydrophilic Compound

[0201] The photo sensitive layer may contain a low-molecular-weight
hydrophilic compound, for the purpose of improving the on-press
developability without degrading the printing durability.

[0031] of Japanese Laid-Open Patent Publication No.
2007-276454, and paragraphs

[0020] to

[0047] of Japanese Laid-Open Patent
Publication No. 2009-154525. The salt may also be potassium salts or
lithium salts.

[0205] The organic sulfate salts are exemplified by sulfate salts of
alkyl, alkenyl, alkynyl, aryl or heterocyclic monoether of polyethylene
oxide. The number of ethylene oxide unit is preferably 1 to 4, and the
salts are preferably sodium salt, potassium salt or lithium salt.
Specific examples thereof include the compounds described in paragraphs

[0207] The low-molecular-weight hydrophilic compound scarcely exhibits a
surfactant activity due to its small size of the hydrophobic portion, so
that fountain solution does not immerse into the exposed area of the
photo sensitive layer (image-forming area) to consequently degrade the
hydrophobicity and film strength of the image-forming area, and thereby
the ink receptivity and printing durability of the image recording layer
are kept at desirable levels.

[0208] The content of the low-molecular-weight hydrophilic compound in the
photo sensitive layer is preferably 0.5 to 20% by mass of the total solid
content of the photo sensitive layer, more preferably 1 to 15% by mass,
and more preferably 2 to 10% by mass. In this range, desirable levels of
on-press developability and printing durability are obtained. The
low-molecular-weight hydrophilic compound may be used alone, or in
combination of two or more species.

[0209] (G) Sensitizer

[0210] The image recording layer may contain a sensitizer such as
phosphonium compound, nitrogen-containing low-molecular-weight compound,
and ammonium group-containing polymer, aiming at improving inking
performance. In particular, for the case where the protective layer
contains an inorganic layered compound, the sensitizer functions as a
surface coating agent of the inorganic layered compound, and prevent the
inking performance from degrading in the process of printing, due to the
inorganic layered compound.

[0037] of Japanese
Laid-Open Patent Publication No. 2008-284858, and the compounds described
in paragraphs

[0030] to

[0057] of Japanese Laid-Open Patent Publication
No. 2009-90645.

[0213] While the ammonium group-containing polymer may be arbitrarily
selected so long as it has an ammonium group in the structure thereof, a
preferable polymer contains, as a copolymerizable component, 5 to 80 mol
% of (meth)acrylate having an ammonium group in the side chain thereof.
Specific examples include the polymers described in paragraphs

[0089] to

[0105] of Japanese Laid-Open Patent Publication No. 2009-208458.

[0214] The ammonium salt-containing polymer preferably has a reduced
specific viscosity (in ml/g), measured by the method of measurement
described below, of 5 to 120, more preferably 10 to 110, and particularly
15 to 100. Mass average molecular weight, converted from the reduced
specific viscosity, is preferably 10,000 to 150,000, more preferably
17,000 to 140,000, and particularly 20,000 to 130,000.

[0215] <<Method of Measuring Reduced Specific Viscosity>>

[0216] In a 20-ml measuring flask, 3.33 g (1 g as solid content) of a 30%
polymer solution is weighed, and the flask is filled up with
N-methylpyrrolidone. The obtained solution is allowed to stand in a
thermostat chamber at 30° C. for 30 minutes, and then placed in a
Ubbelohde reduced viscosity tube (viscometer constant=0.010 cSt/s), and
the time it takes for the solution to elute at 30° C. is measured.
The measurement is repeated twice using the same sample, to thereby find
an average value. The blank (N-methylpyrrolidone only) is also measured
similarly, and the reduced specific viscosity (ml/g) is calculated by the
formula below.

[0227] The content of the sensitizer is preferably 0.01 to 30.0% by mass
of the total solid content of the photo sensitive layer, more preferably
0.01 to 15.0% by mass, and still more preferably 1 to 5% by mass.

[0228] (H) Hydrophobization Precursor

[0229] The image recording layer may contain a hydrophobization precursor,
for the purpose of improving the on-press developability. The
hydrophobization precursor means a fine particle capable of turning, upon
heating, the image recording layer into hydrophobic. The fine particle is
preferably at least one species selected from hydrophobic thermoplastic
polymer particle, thermoreactive polymer particle, polymer particle
having polymerizable group, and microcapsule and microgel (crosslinked
polymer particle) containing hydrophobic compound. Among them, polymer
particle and microgel having polymerizable group are preferable.

[0230] Preferable examples of the hydrophobic thermoplastic polymer
particle include those described in Research Disclosure No. 333003
published in January 1992, Japanese Laid-Open Patent Publication Nos.
H09-123387, H09-131850, H09-171249, H09-171250 and European Patent No.
931647.

[0231] Specific examples of polymer composing the polymer particle include
ethylene, styrene, vinyl chloride, methyl acrylate, ethyl acrylate,
methyl methacrylate, ethyl methacrylate, vinylidene chloride,
acrylonitrile, vinylcarbazole, acrylate or methacrylate having a
polyalkylene structure, all of which being available in the form of
monomer, homopolymer, copolymer and mixture. Among them, more preferable
examples include polystyrene, copolymer containing styrene and
acrylonitrile, and methyl polymethacrylate.

[0232] Average particle size of the hydrophobic thermoplastic polymer
particle used in the present invention is preferably 0.01 to 2.0 μm.

[0233] The thermoreactive polymer particle used in the present invention
is exemplified by polymer particle having a thermoreactive group which
forms a hydrophobic domain as a result of crosslinking by thermal
reaction and concomitant change in the functional group.

[0234] While the thermoreactive group contained in the polymer particle
used in the present invention may be arbitrarily selected from those
capable of proceeding any type of reaction so long as it can form a
chemical bond, it is preferably a polymerizable group. The preferable
examples include ethylenic unsaturated group which undergoes radical
polymerization reaction (acryloyl group, methacryloyl group, vinyl group,
allyl group, etc.); cation polymerizable group (vinyl group, vinyloxy
group, epoxy group, oxetanyl group, etc.); isocyanate group or block
thereof which undergoes addition reaction; epoxy group, vinyloxy group
and functional group containing an activated hydrogen atom reactive with
them (amino group, hydroxy group, carboxyl group, etc.); carboxyl group
which undergoes condensation reaction, and functional group capable of
reacting therewith and having a hydroxy group or amino group; and acid
anhydride which undergoes ring-opening addition reaction, and amino group
or hydroxy group allow to react therewith.

[0235] The microcapsule used in the present invention contains all of, or
a part of, the constituents of the photo sensitive layer, typically as
described in Japanese Laid-Open Patent Publication Nos. 2001-277740 and
2001-277742. The constituents of the image recording layer may also be
contained outside the microcapsule. Still alternatively, the photo
sensitive layer containing microcapsule may be configured so as to
contain the hydrophobic constituents encapsulated in the microcapsule,
and hydrophilic constituents outside the microcapsule.

[0236] The microgel used in the present invention may contain at least
either therein or on the surface thereof, a part of constituents of the
photo sensitive layer. In particular, an embodiment of reactive microgel,
configured by attaching the radical-polymerizable group onto the surface
thereof, is preferable from the viewpoint of image-forming sensitivity
and printing durability.

[0237] Encapsulation of the constituents of the photo sensitive layer into
the microcapsule or microgel is arbitrarily selectable from those known
in the art.

[0238] Average particle size of the microcapsule or microgel is preferably
0.01 to 3.0 μm, more preferably 0.05 to 2.0 μm, and particularly
0.10 to 1.0 μm. Satisfactory levels of resolution and long-term
stability may be ensured in the above-described ranges.

[0239] The content of the hydrophobization precursor is preferably 5 to
90% by mass relative to the total solid content of the photo sensitive
layer.

[0240] (I) Other Components of Image Recording Layer

[0241] The photo sensitive layer preferably contains chain transfer agent.
The chain transfer agent is defined typically in "Kobunshi Jiten (The
Dictionary of Polymer), 3rd Edition" (edited by The Society of Polymer
Science, Japan, 2005) p. 683-684. The chain transfer agent adoptable
herein includes compound having SH, PH, SiH or GeH in the molecule
thereof. These groups may produce a radical by donating a hydrogen to a
low-active radical species, or, may produce a radical after being
oxidized, followed by deprotonation. It is particularly preferable for
the photo sensitive layer to contain a thiol compound (2-mercapto
benzimidazoles, 2-mercapto benzthiazoles, 2-mercapto benzoxazoles,
3-mercapto triazoles, 5-mercapto tetrazoles, etc.).

[0242] The content of the chain transfer agent is preferably 0.01 to 20
parts by mass relative to the total solid content (100 parts by mass) of
the photo sensitive layer, more preferably 1 to 10 parts by mass, and
particularly 1 to 5 parts by mass.

[0243] The photo sensitive layer may further contain various additives as
needed. The additives are exemplified by surfactant for enhancing
developability and improving coating surface texture; hydrophilic polymer
for improving developability and dispersion stability of the
microcapsule; colorant and baking agent for easy discrimination between
the image-forming area and the non-image-forming area; polymerization
inhibitor for avoiding unnecessary thermal polymerization of the
polymerizable compound in the process of manufacturing or storage of the
photo sensitive layer; hydrophobic low-molecular-weight compound such as
higher aliphatic acid derivative for avoiding inhibition of
oxygen-induced polymerization; inorganic particle and organic particle
for improving strength of cured film in the image-forming area;
co-sensitizer for improving the sensitivity; and plasticizer for
improving plasticity. These compounds may be any of those known in the
art, such as those disclosed in paragraphs

[0067] of
Published Japanese Translation of PCT International Publication for
Patent Application No. 2005-509192, and paragraphs

[0023] to

[0026], and

[0059] to

[0066] of Japanese Laid-Open Patent Publication No.
2004-310000. The surfactant may also be those which may be added to the
developer described later.

[0244] (Formation of Photo Sensitive Layer)

[0245] The photo sensitive layer in the lithographic printing plate
precursor according to the present invention may be formed by an
arbitrary method known in the art, without special limitation. The photo
sensitive layer is formed by dispersing or dissolving the above-described
necessary components of the photo sensitive layer into a solvent to
prepare a coating liquid, and then coating the liquid. The solvent
adoptable herein is exemplified by methyl ethyl ketone, ethylene glycol
monomethyl ether, 1-methoxy-2-propanol, 2-methoxyethyl acetate,
1-methoxy-2-propyl acetate, and γ-butyrolactone, but not limited
thereto. The solvent may be used alone, or in combination of two or more
species. The solid content of the coating liquid is preferably 1 to 50%
by mass.

[0247] The copolymer (A) may be incorporated into the photo sensitive
layer or undercoat layer, by adding the copolymer (A) to the coating
liquid for forming the photo sensitive layer, or to the coating liquid
for forming the undercoat layer. For the case where the copolymer (A) is
contained in the photo sensitive layer, the content of the copolymer (A)
(solid content) is preferably 0.1 to 100 mg/m2, more preferably 1 to
30 mg/m2, and still more preferably 5 to 24 mg/m2.

[0248] [Support]

[0249] The support used for the lithographic printing plate precursor
according to the present invention is not specifically limited, provided
that it is plate-like hydrophilic support with dimensional stability.
Aluminum plate is particularly preferable as the support. The aluminum
plate preferably undergoes surface treatment such as roughening or
anodizing prior to use. The surface of aluminum plate may be roughened by
various methods including mechanical roughening, electro-chemical
roughening (eroding the surface by an electro-chemical process), and
chemical roughening (selectively eroding the surface in a chemical
process). Preferable examples of these methods of treatment are descried
in paragraphs

[0241] to

[0245] of Japanese Laid-Open Patent Publication
No. 2007-206217.

[0250] The support preferably has a center line average roughness of 0.10
to 1.2 μm. In this range, the support will exhibit good adhesiveness
with the photo sensitive layer, good printing durability, and good
staining resistance.

[0251] Color density of the support is preferably 0.15 to 0.65 in terms of
reflection density value. In this range, good image forming performance
by virtue of suppressed halation in the process of pattern-wise exposure,
and readiness of plate check after development may be ensured.

[0252] The support is preferably 0.1 to 0.6 mm thick, more preferably 0.15
to 0.4 mm thick, and still more preferably 0.2 to 0.3 mm thick.

<Hydrophilization>

[0253] In the lithographic printing plate precursor according to the
present invention, it is also effective to hydrophilize the surface of
the support, for the purpose of improving the hydrophilicity in the
non-image-forming area and of preventing printing blot.

[0254] Methods of hydrophilization of the surface of the support include
alkali metal silicate treatment by which the support is dipped into an
aqueous solution of sodium silicate or the like, for electrolytic
treatment; treatment using potassium fluorozirconate; and treatment using
polyvinyl phosphonate. The method using an aqueous solution of polyvinyl
phosphonate is preferably used.

[0255] [Extra Layer Optionally Provided Between the Substrate and the
Photosensitive Layer]

In the lithographic printing plate precursor of the present invention, a
primer layer is conveniently provided between the substrate and the
photosensitive layer to improve hydrophilicity of non-image areas and to
prevent print staining.

[0256] <Primer Layer>

When the lithographic printing plate precursor of the present invention
has a primer layer, the primer layer preferably contains the copolymer
(A). In this case, the content of the copolymer (A) is as described for
the content of the copolymer (A) in the photosensitive layer. The primer
layer may further contain additional compounds other than the copolymer
(A), and such additional compounds preferably include the silane coupling
agents containing an addition-polymerizable ethylenic double
bond-reactive group described in JP-A-H10-282679, the phosphorus
compounds containing an ethylenic double bond-reactive group described in
JP-A-H2-304441 and the like. Especially preferred compounds are compounds
having a polymerizable group such as methacryl, allyl and the like and a
substrate-adsorbing group such as sulfonic acid, phosphoric acid,
phosphoric acid ester and the like. Other preferred compounds include
compounds containing a hydrophilicity-conferring group such as ethylene
oxide and the like in addition to the polymerizable group and
substrate-adsorbing group. The primer layer can be provided by applying a
solution of the compound dissolved in water or an organic solvent such as
methanol, ethanol, methyl ethyl ketone or the like or a mixed solvent
thereof on the substrate and drying it, or immersing the substrate in a
solution of the compound dissolved in water or an organic solvent such as
methanol, ethanol, methyl ethyl ketone or the like or a mixed solvent
thereof to allow the compound to be adsorbed, and then washing it with
water or the like and drying it. In the former method, a solution of the
compound at a concentration of 0.005 to 10% by mass can be applied by
various techniques. Any technique can be used, such as bar coating, spin
coating, spray coating, curtain coating and the like, for example. In the
latter method, the concentration of the solution is 0.01 to 20% by mass,
preferably 0.05 to 5% by mass, the immersion temperature is 20 to
90° C., preferably 25 to 50° C., and the immersion time is
0.1 second to 20 minutes, preferably 2 seconds to 1 minute. The coating
mass of the primer layer (expressed as solids) is preferably 0.1 to 100
mg/m2, more preferably 1 to 30 mg/m2.

[0257] [Protective Layer]

[0258] For the purpose of blocking diffusive intrusion of oxygen which may
inhibit the polymerization reaction in the process of exposure to light,
the lithographic printing plate precursor according to the present
invention is preferably provided with the protective layer (oxygen
barrier layer) on the photo sensitive layer. Materials for composing the
protective layer are arbitrarily selectable either from water-soluble
polymer and water-insoluble polymer, and two or more species may be
combined as necessary. More specifically, polyvinyl alcohol, modified
polyvinyl alcohol, polyvinyl pyrrolidone, water-soluble cellulose
derivative, and poly(meth)acrylonitrile are exemplified. Among them,
water-soluble polymer compound is preferably used by virtue of its
relatively good crystallinity. More specifically, a good result may be
obtained by using polyvinyl alcohol as a major constituent, from the
viewpoint of achieving excellent basic performances such as oxygen
barrier performance, and removability in development.

[0259] Polyvinyl alcohol used for the protective layer may partially be
substituted, at the hydroxy groups thereof, by ester, ether or acetal, so
long as a certain amount of unsubstituted vinyl alcohol units, necessary
for ensuring oxygen barrier performance and water-solubility, is
contained. Similarly, polyvinyl alcohol may also contain other
polymerizable component partially in the structure thereof. Polyvinyl
alcohol may be obtained by hydrolyzing polyvinyl acetate. Specific
examples of polyvinyl alcohol include those having a degree of hydrolysis
of 69.0 to 100 mol %, and having a number of polymerizable repeating
units of 300 to 2400. More specific examples include PVA-102, PVA-103,
PVA-105, PVA-110, PVA-117, PVA-117H, PVA-120, PVA-124, PVA-124H, PVA-CS,
PVA-CST, PVA-HC, PVA-203, PVA-204, PVA-205, PVA-210, PVA-217, PVA-220,
PVA-224, PVA-235, PVA-217EE, PVA-217E, PVA-220E, PVA-224E, PVA-403,
PVA-405, PVA-420, PVA-424H, PVA-505, PVA-617, PVA-613, PVA-706 and PVA
L-8, all of which commercially available from Kuraray Co. Ltd. Polyvinyl
alcohol may be used alone, or in the form of mixture. The content of
polyvinyl alcohol in the protective layer is preferably 20 to 95% by
mass, and more preferably 30 to 90% by mass.

[0260] Also modified polyvinyl alcohol may preferably be used. In
particular, acid-modified polyvinyl alcohol having the carboxylate group
or sulfonate group is preferably used. More specifically, preferable
examples include the polyvinyl alcohol described in Japanese Laid-Open
Patent Publication Nos. 2005-250216 and 2006-259137.

[0261] For the case where polyvinyl alcohol is used in a mixed form with
other materials, the materials to be mixed are preferably modified
polyvinyl alcohol, polyvinyl pyrrolidone or a modified product thereof,
from the viewpoint of oxygen barrier performance and readiness of removal
in development. The content in the protective layer is 3.5 to 80% by
mass, preferably 10 to 60% by mass, and more preferably 15 to 30% by
mass.

[0262] The protective layer may be added with several percents, relative
to the polymer, of glycerin, dipropylene glycol or the like so as to give
flexibility. Alternatively, several percents by mass, relative to the
polymer, of anionic surfactants such as the sodium alkyl sulfuric acid
and sodium alkyl sulfonate; ampholytic surfactants such as alkylamino
carboxylate salt, and alkylamino dicarboxylate salt; and nonionic
surfactants such as polyoxyethylene alkyl phenyl ether polymer may be
added.

[0263] In addition, for the purpose of improving the oxygen barrier
performance and surface protective performance of the photo sensitive
layer, the protective layer may contain an inorganic layered compound.
Among the inorganic layered compounds, fluorine-containing swellable
synthetic mica, which is a synthetic inorganic layered compound, is
particularly useful. More specifically, preferable examples include the
inorganic layered compounds described in Japanese Laid-Open Patent
Publication No. 2005-119273.

[0264] The amount of coating of the protective layer is preferably 0.05 to
10 g/m2, and is more preferably 0.1 to 5 g/m2 if the inorganic
layered compound is contained, and whereas more preferably 0.5 to 5
g/m2 if the inorganic layered compound is not contained.

[0265] [Back Coat Layer]

[0266] The lithographic printing plate precursor according to the present
invention may be provided with a back coat layer on the back surface of
the support as necessary. The back coat layer is preferably exemplified
by a cover layer composed of the organic polymer compounds described in
Japanese Laid-Open Patent Publication No. H05-45885, or composed of the
metal oxides described in Japanese Laid-Open Patent Publication No.
H06-35174 which are obtained by allowing organic metal compound or
inorganic metal compound to hydrolyze or undergo polycondensation. Among
them, alkoxy compounds of silicon, such as Si(OCH3)4,
Si(OC2H5)4, Si(OC3H7)4,
Si(CO4H9)4 are preferable in view of inexpensiveness and
availability of the source materials.

Second Embodiment

Lithographic Printing Plate Precursor

[0267] The lithographic printing plate precursor of the present invention
comprises a substrate; a photosensitive layer containing at least (B) a
polymerization initiator; (C) a polymerizable compound and (D) a binder
provided on the substrate; and optionally an extra layer provided between
the substrate and the photosensitive layer, wherein the photosensitive
layer or the extra layer adjacent to the substrate contains (A) a
copolymer different from (D) the binder and wherein the copolymer
comprises (a0) a repeating unit having a structure represented by formula
(a1-0) below in a side chain.

##STR00072##

In formula (a1-0), L1 represents a divalent covalent linking group,
excluding alkylene. Z1 represents a covalent linking group selected
from the group consisting of alkylene, arylene, --O--, --S-- and a
combination thereof, provided that both ends are not --O-- or --S--, and
when L1 is arylene, Z1 is not arylene. X1 represents a
hydrogen atom or an electron-releasing group having a Hammett substituent
constant op value of 0.2 or less. The asterisk (*) indicates the point of
attachment to the main chain of the copolymer. Lithographic printing
plates having excellent developability, handling properties, printing
durability with normal inks and printing durability with UV inks can be
provided by using the lithographic printing plate precursor of the
present invention having the features described above. Preferably, the
lithographic printing plate precursor of the present invention can be
directly converted into a plate using various lasers from digital signals
of computers or the like, i.e., it is applicable to so-called
computer-to-plate. Preferably, it can also be developed in aqueous
solutions at pH 2.0 to 10.0 or less or on a printing press. Preferred
aspects of the lithographic printing plate precursor of the present
invention are explained in detail below.

[0268] The lithographic printing plate precursor of the present invention
comprises a substrate and a photosensitive layer provided on the
substrate.

Further, the lithographic printing plate precursor of the present
invention may optionally comprise an extra layer between the substrate
and the photosensitive layer. The lithographic printing plate precursor
of the present invention preferably comprises a primer layer as the extra
layer. Further, the lithographic printing plate precursor of the present
invention preferably comprises a protective layer on the surface of the
photosensitive layer opposite to the substrate. Further, the lithographic
printing plate precursor of the present invention may comprise a back
coating layer on the bottom of the substrate as appropriate. The
photosensitive layer, extra layer, protective layer, and back coating
layer constituting the lithographic printing plate precursor of the
present invention are explained in order below, and processes for forming
the lithographic printing plate precursor of the present invention are
also explained.

[0269] Photosensitive Layer>

The photosensitive layer of the lithographic printing plate precursor of
the present invention contains at least (B) a polymerization initiator,
(C) a polymerizable compound, and (D) a binder. Further, the lithographic
printing plate precursor of the present invention is characterized in
that the photosensitive layer or the extra layer contains (A) a copolymer
different from (D) the binder wherein the copolymer comprises (a0) a
repeating unit having a structure represented by formula (a1-0) above in
a side chain, i.e., the photosensitive layer may contain the copolymer
(A). When the primer layer described below is provided as the extra layer
between the substrate and the photosensitive layer, the photosensitive
layer may not contain the copolymer (A), but the primer layer may contain
the copolymer (A). However, the primer layer preferably contains the
copolymer (A) in the lithographic printing plate precursor of the present
invention. Further, the photosensitive layer may further contain other
components as appropriate. The components of the photosensitive layer are
explained in detail below.

[0270] (A) Copolymer

In the lithographic printing plate precursor of the present invention,
the photosensitive layer adjacent to the substrate may contain a
copolymer comprising (a0) a repeating unit having a structure represented
by formula (a1-0) below in a side chain. Although the primer layer
preferably contains the copolymer (A) in the lithographic printing plate
precursor of the present invention, the copolymer (A) is described in
detail below in the photosensitive layer for sake of explanation.

##STR00073##

In formula (a1-0), L1 represents a divalent covalent linking group,
excluding alkylene. Z1 represents a covalent linking group selected
from the group consisting of alkylene, arylene, --O--, --S-- and a
combination thereof, provided that both ends are not --O-- or --S--, and
when L1 is arylene, Z1 is not arylene. X1 represents a
hydrogen atom or an electron-releasing group having a Hammett substituent
constant op value of 0.2 or less. The asterisk (*) indicates the point of
attachment to the main chain of the copolymer. The structures of the
repeating units preferably contained in the copolymer (A) and the ratios
of them in the copolymer are explained below.

[0271] (a0) Repeating unit having a structure represented by formula
(a1-0) in a side chain:

First, (a0) the repeating unit having a structure represented by formula
(a1-0) in a side chain is explained. In formula (a1-0) above, the
divalent covalent linking group represented by L1 excludes alkylene.
The divalent covalent linking group represented by L1 is preferably
a divalent linking group selected from the group consisting of --O--,
--S--, --C(═O)--, --SO2--, --NH-- (wherein the hydrogen atom in
--NH--may be replaced by a substituent, and typical examples of
substituents include C1-10 alkyl and C6-15 aryl) or arylene or any
combination of these groups. In the present invention, L1 is
preferably a divalent linking group selected from the group consisting of
--O--, --C(═O)--, --NH--, C6-16 arylene or a combination thereof,
more preferably *--C(═O)--O--, *--C(═O)--NH--, 1,2-phenylene,
1,3-phenylene, 1,4-phenylene, 1,2-naphthalene, 1,5-naphthalene or the
like, even more preferably *--C(═O)--O--, *--C(═O)--NH--,
1,4-phenylene or the like, especially preferably *--C(═O)--NH--. The
asterisk (*) here indicates the point of attachment to the main chain of
the polymer compound, i.e., the copolymer (A). Moreover, the hydrogen
atoms in these groups may be replaced by substituents.

[0272] In formula (a1-0) above, Z1 represents a covalent linking
group selected from the group consisting of alkylene, arylene, --O--,
--S-- and a combination thereof, provided that both ends are not --O--
and --S--, and when L1 is arylene, Z1 is not arylene. As used
herein, alkylene refers to a divalent straight-chain, cyclic or branched
chain saturated hydrocarbon group, and arylene refers to a divalent
monocyclic or polycyclic aromatic hydrocarbon group. Specific examples of
alkylene include, for example, methylene, ethylene, propylene, butylene,
pentylene, hexylene and octylene and the like. Specific examples of
arylene include, for example, 1,2-phenylene, 1,3-phenylene,
1,4-phenylene, biphenyl-4,4'-diyl, diphenylmethane-4,4'-diyl,
3,3'-dimethylbiphenyl-4,4'-diyl, 1,2-naphthalene, 1,5-naphthalene,
2,6-naphthalene and the like. Moreover, the hydrogen atoms in these
groups may be replaced by substituents.

In the present invention, Z1 is preferably methylene, ethylene,
propylene, butylene, pentylene, hexylene, cyclohexane-1,4-diyl,
1,2-phenylene, 1,3-phenylene, 1,4-phenylene, 1,2-naphthalene,
1,5-naphthalene and a linking group composed of two or more of these
divalent linking groups linked through --O-- or --S--, more preferably
methylene, ethylene, propylene, butylene, pentylene, hexylene,
1,3-phenylene, 1,4-phenylene, 1,5-naphthalene and a linking group
composed of two or more of these divalent linking groups linked through
--O--, even more preferably methylene, ethylene, propylene, butylene,
pentylene, 1,4-phenylene, --C2H4--O--C2H4--,
--C2H4--O--C2H4--O--C2H4--,
--C2H4--O-1,4-phenylene-O-1,4-phenylene-O--C2H4.
Moreover, the hydrogen atoms in these groups may be replaced by
substituents.

[0273] In formula (a1-0) above, X1 represents a hydrogen atom or an
electron-releasing group having a Hammett substituent constant op value
of 0.2 or less. The Hammett rule is an experimental rule proposed by L.
P. Hammett in 1935 to quantitatively explain the influence of
substituents on the reaction or equilibrium of benzene derivatives and
currently widely recognized as valid. The substituent constants
determined by the Hammett rule include up value and am value, which can
be found in many standard books and are described in detail in e.g.,
"Lange's Handbook of Chemistry" edited by J. A. Dean, 12th Edition, 1979
(Mc Graw-Hill); and "Fields of Chemistry, Extra Issue", 122, pp. 96-103,
1979 (Nankodo Co., Ltd.). It should be understood that various
substituents herein are defined or described by the Hammett substituent
constant up, but they are not to be construed as being limited to only
substituents having values known from literature found in these books,
but also include even substituents having values unknown from literature
so far as they are within the indicated ranges as determined by the
Hammett rule. The compound of the present invention represented by
formula (1) is not a benzene derivative, but the op value is used herein
as a measure indicating the electronic effect of a substituent
irrespective of the substituted position. Hereinafter, the op value is
used in such meaning. As used herein, the Hammett value is the value
described in "Chemical Seminars 10 Hammett rule--Structure and
Reactivity--Edited by Naoki Inamoto (1983, published by Maruzen Company,
Limited) Specific examples of the electron-releasing group X1
include alkoxy, aryloxy, anilino, monoalkylamino, hydroxy, trialkylsilyl,
trialkylsilyloxy, alkyl, alkenyl, aryl, acylamino, carbamoylamino,
alkoxycarbonylamino, 1-aziridinyl, ferrocenyl, and 3-thienyl.

[0274] When the X1 group is an electron-releasing group, the Hammett
substituent constant op value is preferably in the range of -0.5 to 0.2,
more preferably -0.3 to 0.1.

[0276] In the present invention, X1 is preferably a hydrogen atom,
alkyl or aryl, more preferably a hydrogen atom or alkyl, even more
preferably a hydrogen atom.

[0277] Specific examples of structures represented by formula (a1-0) above
in the present invention are shown below, but the present invention is
not limited to these examples.

##STR00074## ##STR00075##

[0278] The repeating unit (a0) having a structure represented by formula
(a1-0) in a side chain includes (meth)acrylic polymers, styryl polymers,
polyurethane resins, polyvinyl alcohol resins, polyvinyl formal resins,
polyamide resins, polyester resins, epoxy resins and the like.
Especially, (meth)acrylic polymers, and styryl polymers are preferred.
The repeating unit (a0) having a structure represented by formula (a1-0)
in a side chain is preferably a repeating unit represented by formula
(A0) below:

##STR00076##

[0279] In formula (A0), Ra to Rc each independently represent a
hydrogen atom, C1-6 alkyl or halogen atom. The repeating unit (a0)
represents a structure represented by formula (a1-0) above, and is
attached to a carbon atom of the main chain of formula (A0) at the point
indicated by the asterisk (*) in formula (a1-0) above.

[0280] The proportion of (a0) contained in the copolymer (A) is preferably
in the range of 0.01 to 20 mol %, more preferably in the range of 0.01 to
10 mol %, even more preferably in the range of 0.01 to 5 mol % based on
the total repeating units to improve staining resistance and printing
durability.

[0281] (a1) Repeating unit having a structure represented by formula
(a1-1) below in a side chain:

In the lithographic printing plate precursor of the present invention,
the copolymer (A) is preferably a copolymer comprising (a1) a repeating
unit having a structure represented by formula (a1-1) below in a side
chain in addition to the repeating unit (a0).

##STR00077##

In formula (a1-1), L2 represents a divalent covalent linking group,
excluding alkylene. Z2 represents a covalent linking group selected
from the group consisting of alkylene, arylene, --O--, --S-- and a
combination thereof, provided that --O-- and --S-- are not terminal, and
when L1 is arylene, Z1 is not arylene. X2 represents a
hydrogen atom or an electron-releasing group having a Hammett substituent
constant op value of 0.2 or less. R represents a substituent. The
asterisk (*) indicates the point of attachment to the main chain of the
polymer compound, i.e., the copolymer (A)

[0282] In formula (a1-1) above, L2, Z2 and X2 have the same
meanings as defined for L1, Z1 and X1 in formula (a1-0)
above, and also cover similar preferred ranges.

The salts here refer to salts with cations such as alkali metals,
alkaline earth metals, heavy metals and the like or salts with organic
cations such as ammonium ion, phosphonium ion and the like. These
substituents may be further substituted with these substituents.

[0285] In the present invention, the substituent represented by R in
formula (a1-1) above is preferably further substituted with a radically
polymerizable reactive group. Preferred examples of the radically
polymerizable reactive group here include addition-polymerizable
unsaturated bond-containing groups (e.g., (meth)acryloyl,
(meth)acrylamide, (meth)acrylonitrile, allyl, vinyl, vinyloxy, alkynyl
and the like), and chain-transferable functional groups (mercapto and the
like). Among others, addition-polymerizable unsaturated bond-containing
groups are preferred to improve printing durability, more preferably
(meth)acryloyl, (meth)acrylamide, and allyl. As used herein,
(meth)acryloyl refers to acryloyl or methacryloyl, and (meth)acrylamide
refers to acrylamide or methacrylamide. The use of a copolymer having a
radically polymerizable reactive group allows excellent developability to
be achieved in unexposed areas and penetration of developers to be
prevented by polymerization in exposed areas, thereby further improving
adhesion between the substrate and the photosensitive layer.

[0286] Preferably, R represents a group represented by formula (Q) below,
or --(C═O)--NR24--CH2--CH(OH)--R26.

##STR00078##

wherein R21, R22 and R23 each independently represent a
hydrogen atom, halogen atom or C1-8 alkyl. Preferably, R21, R22
and R23 each independently represent a hydrogen atom, C1-6 alkyl or
halogen atom (--F, --Br, --Cl, --I). More preferably, at least two of
R21, R22 and R23 are a hydrogen atom and the remaining one
is a hydrogen atom or C1-6 alkyl. Especially preferably, at least two of
R21, R22 and R23 are a hydrogen atom and the remaining one
is methyl. R24 represents a hydrogen atom, halogen atom or C1-8
alkyl. Further, R26 represents C1-8 alkyl. R24 and R26 may
be further substituted, and preferred substituents include hydroxyl, and
the group represented by formula (Q) above.

[0287] In the present invention, the structure represented by formula
(a1-1) above is preferably a structure generated by the action of a
reactive reagent on a structure represented by formula (a1-0) above. The
structure of formula (a1-1) above can readily be obtained by the action
of a reactive reagent such as, e.g., an acid halide, acid anhydride,
mixed acid anhydride, isocyanic acid compound, epoxy compound, sulfonyl
halide compound or alkyl halide compound or the like on the structure
represented by formula (a1-0) above.

[0288] Specific examples of structures represented by formula (a1-1) above
in (a1) in the present invention are shown below, but the present
invention is not limited to these examples.

##STR00079## ##STR00080## ##STR00081## ##STR00082## ##STR00083##

[0289] The repeating unit (a1) having a struture represented by formula
(a1-1) in a side chain preferably has a similar skeleton to that of the
repeating unit (a0) having a structure represented by formula (a1-0) in a
side chain.

[0290] In the present invention, the proportion of the repeating unit (at)
having a structure represented by formula (a1-1) above in a side chain
based on the total repeating units constituting the copolymer (A) is
preferably 0 to 70 mol, more preferably 1 to 50 mol %, even more
preferably 5 to 40%. When the repeating unit (a1) having a structure
represented by formula (a1-1) above in a side chain is a repeating unit
having a radically polymerizable reactive group, it is preferably
contained at 0 to 50 mol %, more preferably 2 to 30 mol %, even more
preferably 5 to 20%. Proportions of 50 mol % or less are preferred for
convenience of preparation because the gelling tendency may decrease
during synthesis. Further, the repeating unit having a radically
polymerizable reactive group is preferably not excessive to improve
staining resistance because hydrophilicity is less likely to decrease. On
the other hand, printing durability may be more readily improved, if the
unit is not too little. In view of these points, it is preferably
contained at 5 to 20 mol %.

[0291] (a2) Repeating unit having at least one functional group
interacting with the substrate surface:

In addition to the repeating unit (a0) having a structure represented by
formula (a1-0) in a side chain, the copolymer (A) preferably comprises
(a2) a repeating unit having at least one functional group interacting
with the substrate surface. The functional group interacting with the
substrate surface may include, for example, those capable of
participating in an interaction such as ionic bond formation, hydrogen
bond formation or polar interaction with a metal, metal oxide, hydroxyl
or the like present on the anodized or hydrophilized substrate. Specific
examples of functional groups interacting with the substrate surface are
shown below, but the present invention is not limited to the specific
examples below.

##STR00084##

[0292] In the formulae above, R11 to R13 each independently
represent a hydrogen atom, C1-10 alkyl, C2-10 alkenyl, C2-10 alkynyl, or
C6-15 aryl, and M, M1 and M2 each independently represent a
hydrogen atom, a metal atom contained in an alkali metal or an alkaline
earth metal or ammonium. The functional group interacting with the
substrate surface is preferably the carboxylic acid-containing group,
sulfonic acid, phosphoric acid ester or a salt thereof, phosphonic acid
or a salt thereof to improve staining resistance and printing durability.

In the lithographic printing plate precursor of the present invention, it
is preferably a phosphoric acid ester or a salt thereof or a phosphonic
acid or a salt thereof, especially preferably a phosphonic acid or a salt
thereof to further improve staining resistance. More preferred examples
of the functional group interacting with the substrate surface
specifically include the structures shown below, but the present
invention is not limited to the specific examples below. In the formulae
below, the asterisk (*) indicates the point of attachment to the main
chain of the polymer compound.

##STR00085##

[0293] The repeating unit (a2) having at least one functional group
interacting with the substrate surface is preferably a repeating unit
represented by formula (A2) below:

##STR00086##

[0294] In formula (A2) above, Ra' to Rc' each independently
represent a hydrogen atom, C1-6 alkyl or halogen atom. L4 represents
a single bond or a divalent linking group. Q represents the functional
group interacting with the substrate surface.

[0295] The divalent linking group represented by L4 preferably
composed of 1 to 60 carbon atoms, 0 to 10 nitrogen atoms, 0 to 50 oxygen
atoms, 1 to 100 hydrogen atoms and 0 to 20 sulfur atoms. More
specifically, it is a divalent linking group selected from the group
consisting of --O--, --S--, --C(═O)--, --SO2--, --NH-- (wherein
the hydrogen atom in --NH-- may be replaced by a substituent, and typical
examples of substituents include C1-10 alkyl and 6-15 aryl), alkylene or
arylene, or any combination of these groups. The divalent linking group
represented by L4 is preferably a divalent linking group selected
from the group consisting of --O--, --C(═O)--, --NH--, C1-12 alkylene
and C6-16 arylene or a combination thereof, more preferably
*--C(═O)--O--, *--C(═O)--NH--, *--C(═O)--O--
(CH2)2--O--, *--C(═O)--NH--(CH2)2--O--,
*--C(═O)--O-- (CH2)2--O-- (CH2)2--O--,
*--C(═O)--NH-- (CH2)2--O-- (CH2)2--O--,
1,2-phenylene, 1,3-phenylene, 1,4-phenylene, 1,2-naphthalene,
1,5-naphthalene and the like, even more preferably *--C(═O)--O--,
*--C(═O)--NH--, *--C(═O)--O-- (CH2)2--O--,
*--C(═O)--NH--(CH2)2--O--, 1,4-phenylene and the like. The
asterisk (*) here indicates the point of attachment to the main chain of
the copolymer (A). Moreover, the hydrogen atoms in these groups may be
replaced by substituents. In formula (A2) above, the functional group
interacting with the substrate surface represented by Q includes the
specific examples mentioned above, and also covers similar preferred
examples.

[0296] In the copolymer (A), the proportion of the repeating unit (a2)
having at least one functional group interacting with the substrate
surface is preferably in the range of 0 to 99 mol %, more preferably in
the range of 10 to 95 mol %, even more preferably in the range of 10 to
90 mol % based on the total repeating units to improve staining
resistance and printing durability.

[0297] (a3) Repeating unit having a hydrophilic group in a side chain:

In the present invention, the copolymer (A) preferably comprises (a3) a
repeating unit having a hydrophilic group in a side chain. The
hydrophilic group is selected from monovalent or divalent or polyvalent
hydrophilic groups capable of readily forming a hydrogen bond/van der
Waals bond/ionic bond with a water molecule, specifically including
hydroxy, carboxyl, amino, sulfo, positively or negatively charged groups,
zwitterionic groups and metal salts thereof and the like. Among them,
hydroxy, sulfonic acid, alkyleneoxy such as ethyleneoxy and propyleneoxy,
quaternary ammonium, amide, ether bond-containing groups, or salts
obtained by neutralizing acid groups such as carboxylic acid, sulfonic
acid, phosphoric acid and the like, heterocyclic groups containing
positively charged nitrogen atoms and the like are preferred, for
example. These hydrophilic groups may also be used as the repeating unit
(a2) having a structure interacting with the substrate surface in a side
chain.

[0298] In the present invention, the repeating unit (a3) having a
hydrophilic group in a side chain is especially preferably a repeating
unit having a zwitterionic structure in a side chain to confer high
hydrophilicity on the substrate surface of non-image areas.

In the lithographic printing plate precursor of the present invention,
the hydrophilic group contained in the copolymer (A) is preferably
selected from zwitterionic structures represented by formula (a3-1) or
formula (a3-2) below.

[0300] In formula (a3-1) above, R31 and R32 each independently
represent a hydrogen atom, alkyl, alkenyl, alkynyl, aryl or heterocyclyl,
or R31 and R32 may be joined together to form a ring structure,
L31 represents a divalent linking group, and A.sup.- represents an
anion-containing structure. Y3 represents a single bond, or a
divalent linking group selected from the group consisting of --CO--,
--O--, --NH--, a divalent aliphatic group, a divalent aromatic group and
a combination thereof. The asterisk (*) indicates the point of attachment
to the main chain of the polymer compound.

[0301] The ring structure formed by R31 and R32 together is
preferably a 5- to 10-membered ring, more preferably a 5- or 6-membered
ring, and may contain a heteroatom such as oxygen atom and the like.

[0302] Examples of alkyls represented by R31 and R32 include
methyl, ethyl, propyl, octyl, isopropyl, t-butyl, isopentyl,
2-ethylhexyl, 2-methylhexyl, cyclopentyl and the like. Examples of
alkenyls represented by R31 and R32 include vinyl, allyl,
prenyl (e.g., dimethylallyl, geranyl and the like), oleyl and the like.

Examples of alkynyls represented by R31 and R32 include
ethynyl, propargyl, trimethylsilylethynyl and the like. Further, examples
of aryls represented by R31 and R32 include phenyl, 1-naphthyl,
2-naphthyl and the like. Further, examples of heterocyclyls include
furanyl, thiophenyl, pyridinyl and the like.

[0304] Especially preferred examples of R31 and R32 include a
hydrogen atom, methyl, or ethyl because of the resulting effect and
availability.

[0305] The divalent linking group represented by Y3 is a single bond
or a divalent linking group selected from the group consisting of --CO--,
--C--, --NH--, a divalent aliphatic group, a divalent aromatic group and
a combination thereof.

[0306] Specific examples L101 to L116 of Y3 consisting of the
combination described above are shown below. In the examples below, each
group is attached to the main chain at the left end.

[0307] The divalent aliphatic group and the divalent aromatic group
described above refer to include the linking groups mentioned as examples
of the divalent aliphatic group containing 1 to 14 carbon atoms for
Z1, and the linking groups mentioned as examples of the divalent
aromatic group containing 6 to 14 carbon atoms for L1, respectively.
Examples of substituents on the divalent aliphatic group and the divalent
aromatic group include the substituents with which the groups represented
by R31 and R32 may be further substituted.

[0308] Among others, Y3 is preferably a single bond, --CO--, a
divalent aliphatic group, a divalent aromatic group, or the specific
examples L101 to L104 shown above. Further, Y3 is preferably L101 or
L103 shown above, even more preferably L103 to improve staining
resistance. Further, the divalent aliphatic group of L31 is
preferably a straight-chain alkylene containing 2 to 4 carbon atoms, most
preferably a straight-chain alkylene containing 3 carbon atoms for
convenience of synthesis.

[0309] L31 represents a divalent linking group, preferably a linking group
selected from the group consisting of --CO--, --O--, --NH--, a divalent
aliphatic group, a divalent aromatic group and a combination thereof, and
preferably contains or less carbon atoms including carbon atoms of the
optionally present substituents described below. Specific examples
thereof include alkylene (preferably containing 1 to 20 carbon atoms,
more preferably 1 to 10 carbon atoms), and arylene (preferably containing
5 to 15 carbon atoms, more preferably 6 to 10 carbon atoms) such as
phenylene, xylylene and the like. Among others, L31 is preferably a
straight-chain alkylene containing 3 to 5 carbon atoms, more preferably a
straight-chain alkylene containing 4 or 5 carbon atoms, most preferably a
straight-chain alkylene containing 4 carbon atoms to improve staining
resistance. Specific examples of L31 include, for example, the
following linking groups:

[0312] To improve staining resistance, A.sup.- is most preferably
sulfonate. Further, a preferred combination of L31 and A.sup.- in
formula (a1-1) above is a combination of a straight-chain alkylene
containing 4 or 5 carbon atoms and sulfonate, most preferably a
combination of a straight-chain alkylene containing 4 carbon atoms and
sulfonate.

[0313] In a preferred combination, Y3 is L101 or L103 shown above,
R31 and R32 are ethyl or methyl, L31 is a straight-chain
alkylene containing 4 or 5 carbon atoms, and A.sup.- is sulfonate. In a
more preferred combination, Y3 is L103 shown above, R31
and R32 are methyl, L31 is a straight-chain alkylene containing
4 carbon atoms, and A.sup.- is sulfonate. The zwitterionic structure
represented by formula (a3-1) above specifically includes the structures
shown below. In the formulae below, the asterisk (*) indicates the point
of attachment to the main chain of the copolymer (A).

In formula (a3-2), L32 represents a divalent linking group, and
E.sup.+ represents a cation-containing structure. Y4 represents a
single bond, or a divalent linking group selected from the group
consisting of --CO--, --O--, --NH--, a divalent aliphatic group, a
divalent aromatic group and a combination thereof. The asterisk (*)
indicates the point of attachment to the main chain of the copolymer.

[0315] Also in formula (a3-2) above, L32 represents a divalent
linking group preferably selected from the group consisting of --CO--,
--O--, --NH--, a divalent aliphatic group, a divalent aromatic group and
a combination thereof. Specific examples and preferred examples thereof
are the same as mentioned above for the linking group represented by
L31

Y4 has the same meaning as defined for Y3 in formula (a3-1)
above, and also covers similar preferred examples. E.sup.+ represents a
cation-containing structure, preferably a structure containing ammonium
or phosphonium, especially preferably a structure containing ammonium.
Examples of cation-containing structures include trimethylammonio,
triethylammonio, tributylammonio, benzyldimethylammonio,
diethylhexylammonio, (2-hydroxyethyl)dimethylammonio, pyridinio,
N-methylimidazolio, N-acridinio, trimethylphosphonio, triethylphosphonio,
triphenylphosphonio and the like. In a most preferred combination of
L32, Y4 and E.sup.+, L32 is an alkylene containing 2 to 4
carbon atoms, Y4 is L101 or L103 shown above, and E.sup.+ is
trimethylammonio or triethylammonio. The zwitterionic structure
represented by formula (a3-2) specifically includes the structures shown
below. In the formulae below, the asterisk (*) indicates the point of
attachment to the main chain of the copolymer (A).

##STR00093## ##STR00094##

[0316] In the present invention, the repeating unit having a zwitterionic
structure is preferably a repeating unit represented by (A3) below
specifically.

##STR00095##

[0317] wherein R201 to R203 each independently represent a
hydrogen atom, C1-6 alkyl or halogen atom. G represents a side chain
having a zwitterionic structure, preferably a structure represented by
formula (a3-1) or (a3-2) above. Preferred examples and combinations of
formulae (a3-1) and (a3-2) are as described above.

[0318] In formula (A3) above, the side chain G especially preferably has a
structure represented by formula (a3-1)

[0319] In the present invention, the proportion of the repeating unit (a3)
having a hydrophilic group in a side chain based on the total repeating
units constituting the copolymer (A) is preferably in the range of 5 to
95 mol %, more preferably in the range of 5 to 80 mol %, even more
preferably in the range of 10 to 70 mol % to improve hydrophilicity.

[0320] Extra repeating unit:

Further, the copolymer (A) may comprise an extra repeating unit other
than the repeating units described above (hereinafter also referred to as
an "extra repeating unit") as a component of a copolymer. Extra repeating
units that may be contained as such repeating units include repeating
units derived from various known monomers. Preferred examples include
repeating units derived from known monomers such as acrylic acid esters,
methacrylic acid esters, acrylamides, methacrylamides, vinyl esters,
styrenes, acrylic acid, methacrylic acid, acrylonitrile, maleic
anhydride, maleimide and the like. Various properties of the layers such
as film-forming properties, film strength, hydrophilicity,
hydrophobicity, solubility, reactivity, stability and the like can be
improved or controlled as appropriate by introducing the extra repeating
unit into the copolymer (A).

[0326] In the copolymer (A), the proportion of the extra repeating unit is
preferably 0 to 60 mol %, more preferably to 40 mol %, even more
preferably 0 to 30%.

[0327] (Weight Average Molecular Weight)

The weight average molecular weight (Mw) of the copolymer (A) can be
appropriately selected depending on the performance design of the
lithographic printing plate precursor. To improve printing durability and
staining resistance, the weight average molecular weight is preferably
2,000 to 1,000,000, more preferably 2,000 to 500,000, most preferably
8,000 to 300,000.

[0328] Specific examples of the copolymer (A) are shown below along with
their weight average molecular weights, but the present invention is not
limited to these examples. It should be noted that the composition ratio
of the polymer structures are expressed in molar percentage.

The copolymer (A) can be synthesized by known methods, but preferably by
using radical polymerization followed by ureation reaction using the
amino group in a polymer side chain and an isocyanate having a radically
polymerizable reactive group.

[0330] Typical techniques for radical polymerization are described in, for
example, "New Polymer Experimental Chemistry, vol. 3" (Edited by the
Society of Polymer Science, Japan, published by KYORITSU SHUPPAN CO.,
LTD., Mar. 28, 1996); "Synthesis and Reaction of Polymers, vol. 1"
(Edited by the Society of Polymer Science, Japan, published by KYORITSU
SHUPPAN CO., LTD., May 1992); "New Textbook of Experimental Chemistry,
vol. 19, Polymer Chemistry (I) (Edited by the Chemical Society of Japan,
published by Maruzen Company, Limited, Nov. 20, 1980); "Textbook of
Material Engineering, Polymer Synthetic Chemistry" (published by Tokyo
Denki University Press, September 1995) and the like, and these
techniques can be applied.

[0331] (B) Polymerization Initiator

The polymerization initiator (hereinafter also referred to as an
"initiator compound") used in the present invention is contained in the
photosensitive layer. In the present invention, a radical polymerization
initiator is preferably used. The preferred range and amount to be added
and the like of the polymerization initiator can be determined by
reference to the description of the first embodiment hereinabove.

[0332] (C) Polymerizable Compound

The preferred range and amount to be added and the like of the (C)
polymerizable compound used in the photosensitive layer can be determined
by reference to the description of the first embodiment hereinabove.

[0333] (D) Binder

The preferred range and amount to be added and the like of the (D) binder
contained in the photosensitive layer of the lithographic printing plate
precursor of the present invention can be determined by reference to the
description of the first embodiment hereinabove.

[0334] (E) Sensitizing Dye

The photosensitive layer preferably contains a sensitizing dye. The
preferred range and amount to be added and the like of the (E)
sensitizing dye used in the photosensitive layer of the lithographic
printing plate precursor of the present invention can be determined by
reference to the description of the first embodiment hereinabove.

[0335] (F) Other Components in the Photosensitive Layer

The photosensitive layer can further contain various additives, as
appropriate. The additives that can be added include surfactants for
promoting developability and improving the profile of coating surfaces,
microcapsules for improving both developability and printing durability,
hydrophilic polymers for improving developability or improving dispersion
stability of microcapsules or the like, colorants or printing-out agents
for visually identifying image areas and non-image areas, polymerization
inhibitors for inhibiting undesired thermal polymerization of radically
polymerizable compounds during preparation or storage of the
photosensitive layer, higher fatty acid derivatives for preventing
polymerization inhibition by oxygen, inorganic microparticles for
improving the strength of cured films of image areas, hydrophilic
low-molecular weight compounds for improving developability,
co-sensitizers or chain transfer agents for improving sensitivity,
plasticizers for improving plasticity and the like. All these compounds
are known and available, including e.g., the compounds described in
paragraphs

[0161] to

[0215] of JP-A2007-206217.

[0336] (Formation of the Photosensitive Layer)

The photosensitive layer in the lithographic printing plate precursor of
the present invention can be formed by any known method without specific
limitation. Specifically, further information can be found in the
description of the first embodiment hereinabove.

[0337] Substrate

The substrate used in the lithographic printing plate precursor of the
present invention is not specifically limited, and any hydrophilic
plate-like substrates having a stable size may be used. Specifically,
further information can be found in the description of the first
embodiment hereinabove.

[0338] <Hydrophilization>

In the lithographic printing plate precursor of the present invention,
the surface of the substrate may preferably be hydrophilized to improve
hydrophilicity and prevent print staining in non-image areas.
Specifically, further information can be found in the description of the
first embodiment hereinabove.

[0339] [Extra Layer Optionally Provided Between the Substrate and the
Photosensitive Layer]

In the lithographic printing plate precursor of the present invention, a
primer layer may preferably be provided between the substrate and the
photosensitive layer to improve hydrophilicity and prevent print staining
in non-image areas.

[0340] <Primer Layer>

When the lithographic printing plate precursor of the present invention
comprises a primer layer, the primer layer preferably contains the
copolymer (A). Details of the primer layer can be found in the
description of the first embodiment hereinabove.

[0341] [Protective Layer]

In the lithographic printing plate precursor of the present invention, a
protective layer (oxygen barrier layer) is preferably provided on the
photosensitive layer to block diffusion and penetration of oxygen
detrimental to polymerization reaction during exposure. Details of the
protective layer can be found in the description of the first embodiment
hereinabove.

[0342] [Back Coating Layer]

The lithographic printing plate precursor of the present invention may
comprise a back coating layer on the bottom of the substrate as
appropriate. The back coating layer preferably includes, for example, the
coating layers made of an organic polymer compound described in
JP-A-H5-45885 or a metal oxide obtained by hydrolyzing and polycondensing
an organic metal compound or an inorganic metal compound described in
JP-A-H6-35174. Among them, silicon alkoxide compounds such as
Si(OCH3)4, Si(OC2H5)4, Si(OC3H7)4, and
Si(OC4H9)4 are preferably used because the source
materials are inexpensive and readily available.

[0343] [Processes for Preparing Lithographic Printing Plates]

First Embodiment

[0344] Lithographic printing plates can be prepared by image-exposing a
lithographic printing plate precursor according to the first embodiment
of the present invention and developing it. An example of a process for
preparing a lithographic printing plate according to a first embodiment
of the present invention comprises: image-exposing a lithographic
printing plate precursor of the present invention; and developing the
exposed lithographic printing plate precursor in a developer having a pH
of 2 to 14; wherein the developing comprises removing unexposed areas of
the photosensitive layer and the protective layer simultaneously in the
presence of the developer.

[0345] Preferably, the process for preparing a lithographic printing plate
of the present invention comprises forming a protective layer on the
surface of the photosensitive layer opposite to the substrate; wherein
the developing comprises removing the photosensitive layer in unexposed
areas and the protective layer simultaneously in the presence of the
developer further containing a surfactant without including
water-washing.

Another example of the process for preparing a lithographic printing
plate according to the first embodiment of the present invention
comprises: image-exposing a lithographic printing plate precursor of the
present invention; and supplying a printing ink and a dampening water to
remove the photosensitive layer in unexposed areas on a printing press.
Preferred aspects of each of the process for preparing a lithographic
printing plate according to the first embodiment of the present invention
are explained in order below. Additionally, lithographic printing plates
can also be prepared from the lithographic printing plate precursor of
the present invention by the process for preparing a lithographic
printing plate of the present invention when the developing includes
water-washing.

[0346] <Exposure>

[0347] The method of manufacturing the lithographic printing plate of the
present invention includes exposing the lithographic printing plate
precursor according to the present invention in a pattern-wise manner.
The lithographic printing plate precursor according to the present
invention is exposed by laser shot through a transparent original having
a line image or halftone image or the like, or laser scanning modulated
by digital data.

[0348] Wavelength of light source is preferably 300 to 450 nm or 750 to
1400 nm. When the light source of 300 to 450 nm is used, the lithographic
printing plate precursor preferably contains, in the photosensitive layer
thereof, a sensitizing dye showing an absorption maximum in this
wavelength. On the other hand, for the case where the light source of 750
to 1400 nm is used, the lithographic printing plate precursor preferably
contains, in the photosensitive layer thereof, an infrared absorber,
which is a sensitizing dye showing an absorption maximum in this
wavelength range. The light source of 300 to 450 nm is preferably a
semiconductor laser. The light source of 750 to 1400 nm is preferably a
solid-state laser or semiconductor laser capable of emitting infrared
radiation. The infrared laser preferably has an output of 100 mW or
larger, exposure time per pixel is preferably 20 microseconds or shorter,
and exposure energy is preferably 10 to 300 mJ/cm2. A multi-beam
laser device is preferably used in order to shorten the exposure time. An
exposure mechanism may be based on Any of internal drum system, external
drum system, and flat bed system.

[0349] The pattern-wise exposure may be proceeded by a general method
using a plate setter, for example. When the on-machine development is
adopted, the lithographic printing plate precursor may be set on a
printing machine and may be exposed pattern-wise on the printing machine.

[0350] <Development>

[0351] The development may be implemented by (1) a method of development
using a developer of pH2 to 14 (developer process), or (2) a method of
development on a printing machine, while feeding fountain solution and/or
ink (on-machine development).

[0352] (Developer Process)

[0353] In the developer process, the lithographic printing plate precursor
is treated using the developer of pH2 to 14, so as to remove the
unexposed area of the photosensitive layer, and thereby lithographic
printing plate is manufactured.

[0354] In a general process of development using a strong alkaline
developer (pH12 or above), the protective layer is removed by pre-water
washing, subjected to alkaline development, post-water washing for
removing alkali by water washing, gum solution treatment, and drying
process, to thereby obtain the lithographic printing plate. According to
a first preferable embodiment of the present invention, the developer
used herein has pH value of 2 to 14. In this embodiment, the developer
preferably contains a surfactant or water-soluble polymer compound, so as
to concomitantly allow the development and gum solution treatment to
proceed. Accordingly, the post-water washing is not indispensable, and
the development and the gum solution treatment may be proceeded in a
single solution.

[0355] Also the pre-water washing is not indispensable, so that also the
removal of the protective layer may be proceeded concomitantly with the
gum solution treatment. In the method of manufacturing the lithographic
printing plate of the present invention, the development and gum solution
treatment is preferably followed by removal of excessive developer using
a squeeze roller for example, and drying.

[0356] The development by developer in the lithographic printing plate
precursor of the present invention may be proceeded as usual at 0 to
60° C., preferably 15 to 40° C. or around, typically by a
method of dipping the exposed lithographic printing plate precursor into
a developer followed by rubbing with a brush, or a method of spraying a
developer followed by rubbing with a brush.

[0357] The development using the developer is successfully implemented on
an automatic processor, equipped with a developer feeder and a rubbing
member. The automatic processor having rotating brush rollers as the
rubbing member is particularly preferable. The automatic processor
preferably has a unit for removing excessive developer, such as squeeze
rollers, and a drying unit such as a hot air blower, on the downstream
side of the developing unit. Moreover, the automatic processor may have a
pre-heating unit for heating the exposed lithographic printing plate
precursor, on the upstream side of the developing unit.

[0358] An example of automatic processor used for the method of
manufacturing a lithographic printing plate of the present invention will
be briefed below, referring to FIG. 1.

[0359] The example of the automatic processor used for the method of
manufacturing a lithographic printing plate of the present invention is
illustrated in FIG. 1. The automatic processor illustrated in FIG. 1 is
basically composed of a developing unit 6 and a drying unit 10, wherein
the lithographic printing plate precursor 4 is developed in the
developing tank 20, and dried in the drying unit 10.

[0360] The automatic processor 100 illustrated in FIG. 2 is composed of a
chamber shaped by an equipment frame 202, and has a pre-heating section
200, a developing section 300 and a drying section 400 aligned in line in
the direction of a feed path 11 along which the lithographic printing
plate precursor is fed (indicated by arrow A).

[0361] The pre-heating section 200 has a heating chamber 208 with a
feeding port 212 and an output port 218, and has tandem rollers 210,
heaters 214 and a circulating fan 216 arranged therein.

[0362] The developing section 300 is partitioned by an outer panel 310
from the pre-heating section 200, and the outer panel 310 has an
insertion slit 312.

[0363] Inside the developing section 300, there is provided a process tank
306 having therein a developing tank 308 filled with a developer, and an
insertion roller pair 304 for guiding the lithographic printing plate
precursor into the process tank 306. The upper portion of the developing
tank 308 is covered with a shielding lid 324.

[0364] Inside the developing tank 308, there is provided a guide roller
344 and a guiding member 342, an immersed roller pair 316, a brush roller
pair 322, a brush roller pair 326, and an output roller pair 318 which
are aligned in sequence from the upstream side of the feeding direction.
The lithographic printing plate precursor brought into the developing
tank 308 is dipped in the developer, and allowed to pass through the
rotating brush roller pairs 322, 326, to be removed with the
non-image-forming area.

[0365] Below the brush roller pairs 322, 326, there is provided a spray
pipe 330. The spray pipe 330 is connected to a pump (not illustrated),
and the developer in the developing tank 308 sucked up by the pump is
ejected through the spray pipe 330 into the developing tank 308.

[0366] On the sidewall of the developing tank 308, there is provided an
overflow port 51 opened at the top end portion of a first circulating
pipe C1, so as to allow an excessive portion of the developer to flow
into the overflow port 51, run down through the first circulating pipe
Cl, to be discharged into an external tank 50 provided outside the
developing section 300.

[0367] The external tank 50 is connected to a second circulating pipe C2.
The second circulating pipe C2 is provided with a filter unit 54 and a
developer feed pump 55. By the developer feed pump 55, the developer is
fed from the external tank 50 to the developing tank 308. The external
tank 50 is provided with a upper level gauge 52 and a lower level gauge
53.

[0368] The developing tank 308 is connected through a third circulating
pipe C3 to a supplementary water tank 71. The third circulating pipe C3
is provided with a water supplement pump 72 by which water reserved in
the supplementary water tank 71 is fed to the developing tank 308.

[0369] A liquid temperature sensor 336 is provided on the upstream side of
the immersed roller pair 316, and a level gauge 338 is provided on the
upstream side of the output roller pair 318.

[0370] A partition board 332 placed between the developing section 300 and
the drying section 400 has an insertion slit provided thereto. On a path
between the developing section 300 and the drying section 400, there is
provided a shutter (not illustrated) which closes the path when the
lithographic printing plate precursor 11 does not travel on the path.

[0371] The drying section 400 has a support roller 402, ducts 410, 412, a
feed roller pair 406, ducts 410, 412, and a feed roller pair 408 aligned
therein in sequence. Each of the ducts 410, 412 has a slit hole 414
provided to the tip thereof. The drying section 400 has provided thereto
an unillustrated drying unit such as a hot air blower, heat generator or
the like. The drying section 400 has a discharge port 404, through which
the lithographic printing plate dried by the drying unit is ejected.

[0372] In the present invention, the developer used for the development by
developer is preferably an aqueous solution of pH2 to 14, or contains a
surfactant. The developer is preferably an aqueous solution mainly
composed of water (with a water content of 60% by mass or more), wherein
an aqueous solution containing a surfactant (anionic, nonioic, cationic,
ampholytic ion-based, etc.), or an aqueous solution containing a
water-soluble polymer compound is particularly preferable. Also an
aqueous solution containing both of surfactant and water-soluble polymer
compound is preferable. The developer is preferably pH3.5 to 13, more
preferably pH6 to 13, and particularly pH6.5 to 10.5. In particular, for
the case where the developer of pH2.0 to 10.0 is used, it is difficult to
concomitantly preventing all of staining resistance, printing durability,
and long-term staining resistance from degrading. The reason why may be
explained as below. When species of the developer is tried to change,
while leaving the material for composing the lithographic printing plate
precursor unchanged, the developer of pH2.0 to 10.0 will degrade the
staining resistance of the unexposed area, as compared with the case
where the conventional alkali developer of pH12 to 13 was used.

[0374] The cationic surfactant used for the developer in the present
invention is arbitrarily selectable from those known in the art, without
special limitation. The examples include alkylamine salts, quaternary
ammonium salts, alkylimidazolinium salt, polyoxyethylene alkylamine
salts, and polyethylene polyamine derivative.

[0376] The ampholytic-ion-based surfactant used for the developer in the
present invention is not specifically limited, and is selectable from
amine oxide-based surfactant such as alkyldimethylamine oxide;
betaine-based surfactant such as alkyl betaine; and amino acid-based
surfactant such as sodium salt of alkylaminofatty acid. In particular,
alkyl dimethylamine oxide which may have a substituent group, alkyl
carboxybetaine which may have a substituent group, and alkyl sulfobetaine
which may have a substituent group are preferably used. More
specifically, the compounds represented by the formula (2) in paragraph

[0256] of Japanese Laid-Open Patent Publication No. 2008-203359; the
compounds represented by the formula (I), formula (II) and formula (VI)
in paragraph

[0028] of Japanese Laid-Open Patent Publication No.
2008-276166; and the compounds described in paragraphs

[0022] to

[0029]
of Japanese Laid-Open Patent Publication No. 2009-47927 may be used.

[0377] Two or more species of the surfactant may be used in the developer.
The content of the surfactant contained in the developer is preferably
0.01 to 20% by mass, and more preferably 0.1 to 10% by mass.

[0379] The soybean polysaccharides are selectable from those known in the
art, such as those commercially available under the trade name of
Soyafive (from Fuji Oil Co. Ltd.) with a variety of grades. Among them,
those showing a viscosity of a 10% by mass aqueous solution of 10 to 100
mPa/sec are preferably used.

[0380] Also the modified starch is selectable from those known in the art,
which may be prepared for example by decomposing starch derived from
corn, potato, tapioca, rice, wheat or the like by acid or enzyme, so as
to give molecules having 5 to 30 glucose residues, and by adding thereto
oxypropylene in an alkaline solution.

[0381] Two or more species of the water-soluble polymer compounds may be
used in the developer. The content of the water-soluble polymer compound
in the developer is preferably 0.1 to 20% by mass, and more preferably
0.5 to 10% by mass.

[0382] The developer used in the present invention may contain a pH
buffering agent. For the developer of the present invention, the pH
buffering agent is arbitrarily selectable without special limitation, so
long as it exhibits a buffering action in the range from pH2 to 14. In
the present invention, a weak alkaline buffering agent is preferably
used, wherein the examples include (a) carbonate ion and hydrogen
carbonate ion, (b) borate ion, (c) water-soluble amine compound and ion
thereof, and combination of these ions. More specifically, (a)
combination of carbonate ion and hydrogen carbonate ion, (b) borate ion,
or (c) combination of water-soluble amine compound and ion thereof, for
example, exhibits a pH buffering action in the developer, capable of
suppressing pH from fluctuating even if the developer is used over a long
period, and is therefore capable of suppressing degradation in the
developability and generation of development scum due to fluctuation in
pH. In the method of manufacturing the lithographic printing plate of the
present invention, the combination of carbonate ion and hydrogen
carbonate ion is particularly preferable.

[0383] In order to allow carbonate ion and hydrogen carbonate ion to
reside in the developer, one possible method is to add a carbonate salt
and a hydrogen carbonate salt into the developer, and another method is
to adjust pH after the carbonate salt or hydrogen carbonate salt are
added, so as to generate carbonate ion or hydrogen ion. While the
carbonate salt and the hydrogen carbonate salt are not specifically
limited, alkali metal salt is preferable. The alkali metal is exemplified
by lithium, sodium, and potassium, wherein sodium is particularly
preferable. The alkali metal may be used alone, or in combination of two
or more species.

[0384] Total content of carbonate ion and hydrogen carbonate ion is
preferably 0.05 to 5 mol/L in the developer, more preferably 0.07 to 2
mol/L, and particularly 0.1 to mol/L.

[0386] Two or more species of the organic solvent may be contained in the
developer. If the organic solvent is not water-soluble, it may be used
after solubilizing it into water with the aid of the surfactant or the
like. When the developer contains the organic solvent, the content of the
organic solvent is preferably less than 40% by mass, from the viewpoint
of safety and inflammability.

[0387] Besides the above-described components, the developer of the in the
present invention may also contain antiseptic, chelating compound,
defoamer, organic acid, inorganic acid, inorganic salt and so forth. More
specifically, the compounds described in paragraphs

[0388] In the present invention, the developer may be used both as a
developer and a supplementary developer for the lithographic printing
plate precursor. It is also preferably adoptable to the automatic
processor described in the above. In the process of development on the
automatic processor, since the developer is exhausted with the progress
of development, so that the supplementary solution or fresh developer may
be used to restore the process capacity.

[0389] <On-Machine Development System>

In the on-machine development system, the lithographic printing plate
precursor after pattern-wise exposure is fed, on a printing machine, with
an oil-based ink and water-based component, so as to remove the
photosensitive layer selectively in the non-image-forming area, to
thereby give a lithographic printing plate.

[0390] More specifically, the lithographic printing plate precursor is
exposed pattern-wise and then set on the printing machine without
development, or, the lithographic printing plate precursor is set on the
printing machine and then exposed pattern-wise on the printing machine.
Next, printing is started by feeding the oil-based ink and the
water-based component. In the non-image-forming area, the uncured
photosensitive layer is removed in the early stage of printing, by
dissolution or dispersion with the aid of the oil-based ink and/or
water-based component fed thereto, and thereby the hydrophilic surface
exposes in the area. On the other hand, in the light-exposed area, the
photosensitive layer cured by exposure forms an acceptance sites for
oil-based ink where a lipophilic surface exposes. While it is arbitrary
which of the oil-based ink and the water-based component is the first to
be fed onto the surface of plate, it is more preferable to feed the
oil-based ink first, in view of preventing the water-based component from
being contaminated by components of the removed photosensitive layer. In
this way, the lithographic printing plate precursor is developed on the
printing machine, and is directly used in a large number of impressions.
The oil-based ink and the water-based component are preferably a printing
ink and fountain solution, respectively, which are used for general
planographic printing.

[0391] In the method of manufacturing a lithographic printing plate from a
lithographic printing plate precursor according to the present invention,
the entire surface of the lithographic printing plate precursor may be
heated before exposure, or during exposure, or between exposure and
development, irrespective of the development style. By the heating, the
image forming reaction in the recording layer may be accelerated, to
thereby advantageously improve the sensitivity and printing durability,
and stabilize the sensitivity. For the development by developer, it is
also effective to subject the developed plate to post-heating or exposure
over the entire surface, aiming at improving the strength of the
image-forming area and printing durability. In general, the pre-heating
is preferably proceeded under a mild condition typically at 150°
C. or lower. Too high temperature may result in curing of the
non-image-forming area. On the other hand, the post-heating after
development needs a very strong condition, typically at 100 to
500° C. Too low temperature may result in insufficient strength of
the image-forming area, whereas too high temperature may degrade the
support, or decompose the image-forming area.

Second Embodiment

[0392] Alternatively, lithographic printing plates can be prepared by
image-exposing a lithographic printing plate precursor according to the
second embodiment of the present invention and developing it. Preferred
aspects of each of the process for preparing a lithographic printing
plate according to the second embodiment of the present invention are
explained in order below. Additionally, lithographic printing plates can
also be prepared from the lithographic printing plate precursor of the
present invention when the developing includes a water-washing though
such a variation departs from the original purpose of the process for
preparing a lithographic printing plate of the present invention.

[0393] <Exposure>

The process for preparing a lithographic printing plate of the present
invention comprises image-exposing a lithographic printing plate
precursor of the present invention. Details of the exposure can be found
in the description of the first embodiment hereinabove.

[0394] <Developing>

The process for preparing a lithographic printing plate of the present
invention comprises developing the exposed lithographic printing plate
precursor in a developer containing a surfactant, wherein the developing
comprises removing unexposed areas of the photosensitive layer and the
protective layer simultaneously in the presence of the developer. Such a
development process using a developer is referred to as developer
process. In the developer process, the image-exposed lithographic
printing plate precursor is treated with a developer containing a
surfactant, whereby the photosensitive layer in unexposed areas is
removed to prepare a lithographic printing plate. The process for
preparing a lithographic printing plate of the present invention may or
may not comprise water-washing, but preferably does not comprise
water-washing. Conventional development processes using highly alkaline
developers (pH 12 or more) typically comprise removing the protective
layer by pre-washing with water, then alkaline development, washing away
the alkali by post-washing with water, treatment with a gum solution, and
drying to prepare a lithographic printing plate. In contrast, a preferred
aspect of the process for preparing a lithographic printing plate of the
present invention does not comprise these water-washing. The developer
containing a surfactant allows development and gum solution treatment to
be performed simultaneously, and eliminates the necessity of post-washing
with water, whereby development and gum solution treatment can be
performed with only one chemical solution. Further, it also eliminates
the necessity of pre-washing with water, whereby removal of the
protective layer can also be performed simultaneously with development
and gum solution treatment. According to a preferred aspect of the
present invention, a developer having a pH of 2.0 to 10.0 is used. In
this aspect, the developer preferably contains a surfactant, or a
surfactant and a water-soluble polymer compound, whereby development and
gum solution treatment take place simultaneously using only one chemical
solution. Further, even when a developer having a pH of 2.0 to 10.0 is
used, pre-washing with water may not be required so that removal of the
protective layer can also take place simultaneously with development and
gum solution treatment. In the process for preparing a lithographic
printing plate of the present invention, the development and gum solution
treatment are preferably followed by removal of an excess of the
developer by using, for example, a squeeze roller, and then drying.

[0395] The developer process of the lithographic printing plate precursor
in the present invention can be performed according to standard methods
at a temperature of 0 to 60° C., preferably 15 to 40° C. or
so, by immersing the exposed lithographic printing plate precursor in a
developer and wiping it with a brush, or by spraying it with a developer
and wiping it with a brush or the like, for example.

[0396] The development with a developer containing a surfactant in the
present invention can be conveniently performed in an automatic
developing machine equipped with a developer feeding means and a wiping
member. An automatic developing machine using a rotating brush roll as a
wiping means is especially preferred. Further, the automatic developing
machine preferably comprises a means for removing an excess of the
developer such as a squeeze roller or a drying means such as a hot-air
heater downstream of the developing means. Further, the automatic
developing machine may comprise a preheating means for heating the
image-exposed lithographic printing plate precursor upstream of the
developing means.

[0397] Examples of automatic developing machines used in the process for
preparing a lithographic printing plate of the present invention are the
same as described for the first embodiment.

[0398] The developer used for the developer process in the present
invention contains a surfactant. The developer is preferably an aqueous
solution containing a major proportion of water (containing 60% by mass
or more of water) Especially, it is preferably an aqueous solution
containing a surfactant (anionic, nonionic, cationic, zwitterionic or the
like) at pH 2.0 to 10.0 or an aqueous solution containing a water-soluble
polymer compound. Also, it is preferably an aqueous solution containing
both surfactant and water-soluble polymer compound. The pH of the
developer is more preferably 3.5 to 10.0, even more preferably 6 to 10.0,
especially preferably 6.5 to 10.0. Especially in the method using a
developer at pH 2.0 to 10.0, it is very difficult to satisfy staining
resistance, printing durability, and developability simultaneously. The
reason for this can be explained as follows. When the same material for a
lithographic printing plate precursor is used with varying types of
developers, developability and staining resistance in unexposed areas
deteriorate with developers at pH 2.0 to 10.0 as compared with
conventional alkaline developers at pH 12 to 13. If the hydrophilicity of
the material is increased to improve developability and staining
resistance with developers at pH 2.0 to 10.0, printing durability tends
to deteriorate. However, such developers at pH 2.0 to 10.0 can
conveniently be used by employing the lithographic printing plate
precursor of the present invention.

[0399] Examples of surfactants used in the developer in the present
invention include the cationic surfactants, nonionic surfactants and
zwitterionic surfactants described in the first embodiment and also cover
the same preferred ranges.

[0400] Two or more of the surfactants may be used in the developer. The
amount of the surfactants contained in the developer is preferably 0.01
to 20% by mass, more preferably 0.1 to 10% by mass.

[0401] Details of the water-soluble polymer compound used in the developer
in the present invention can be found in the description of the first
embodiment.

[0402] The developer used in the present invention may contain a pH
buffering agent. Details of the pH buffering agent can be found in the
description of the first embodiment.

[0403] In the present invention, the developer may contain an organic
solvent. Details of the organic solvent can be found in the description
of the first embodiment.

[0404] In the present invention, the developer may contain preservatives,
chelating compounds, defoamers, organic acids, inorganic acids, inorganic
salts and the like in addition to the components mentioned above.
Specifically, the compounds described in paragraphs

[0266] to

[0270] of
JP-A2007-206217 can preferably be used.

[0405] In the present invention, the developer can be used as a developer
and a replenishment developer for the exposed lithographic printing plate
precursor. Further, it can preferably be applied to the automatic
developing machine as described above. In the case of development using
an automatic developing machine, the developer fatigues with the number
of cycles so that the throughput may be recovered by using the
replenishment developer or a fresh developer.

[0406] (Miscellaneous)

In the process for preparing a lithographic printing plate from the
lithographic printing plate precursor of the present invention, the
lithographic printing plate precursor may be totally heated before
exposure, during exposure or between exposure and development, if
desired. Such heating may promote image-forming reaction in the
photosensitive layer, leading to benefits such as improvements in
printing durability and stabilization of sensitivity. In the case of the
developer process, the overall postheating or overall exposure of the
developed image is also effective to improve image fastness and printing
durability. Typically, heating before development preferably takes place
under mild conditions of 150° C. or less. If the temperature is
too high, non-image areas may be hardened or other problems may occur.
Heating after development takes place under very vigorous conditions,
typically in the range of 100 to 500° C. If the temperature is
low, sufficient effect on image fastness cannot be obtained, but if it is
too high, such problems as substrate degradation or thermal degradation
of image areas may occur.

[0407] Features of the present invention will further be detailed
referring to Examples. Note that the amount of use, ratio, details of
processes, and procedures of processes described in Examples below may be
arbitrarily modified, without departing from the spirit of the present
invention. The scope of the present invention is, therefore, not
restrictively understood by the specific examples described below.

Example A

Synthesis Example of Copolymers 1

<Synthesis of Specific Polymer Compound P-1-4>

[0408] A 500-ml three-neck flask was charged with 1.98 g of
dimethyl-N-methacryloyloxyethyl-N-carboxymethyl-ammonium betaine (from
Osaka Organic Chemical Industry Ltd.), 9.68 g of 2-(phosphonooxy)ethyl
methacrylate (from Kyoeisha Chemical Co., Ltd.), 8.34 g of
2-methacrylamide ethylamine (synthetic product), and 40 g of distilled
water, and the mixture was heated with stirring for 10 minutes at
60° C. under a stream of nitrogen gas. Then, 0.9 g of the
polymerization initiator VA-046B (from Wako Pure Chemical Industries,
Ltd.) was dissolved in 40 g of distilled water, and added dropwise over 3
hours. Then, 0.9 g of VA-046B was added again, and the mixture was heated
at 80° C. for 3 hours, and then cooled. The resulting polymer
solution was adjusted to pH 9.7 by adding NaOH. Then, 0.2 g of 4-OH TEMPO
(from Tokyo Chemical Industry Co., Ltd.) was added, and the mixture was
heated to 55° C., and 30.22 g of methacrylic anhydride (from
Aldrich) was added dropwise over 1 hour. After completion of the dropwise
addition, the mixture was kept at 55° C. for 6 hours. Then, 500 g
of ethyl acetate was added, and the lower layer was collected. To the
collected lower layer was added 15 g of the ion exchange resin Amberlyst
R15 (from Aldrich), and the mixture was stirred at room temperature for 2
hours, and then Amberlyst R15 was removed by filtration to give an
aqueous solution of specific polymer compound P-1-4. The weight average
molecular weight (Mw) of the resulting specific polymer compound P-1-4
was determined to be 120,000 by Gel Permeation Chromatography (GPC) using
polyethylene glycol as standard.

[0409] <Synthesis of Specific Polymer Compound P-1-54>

A 500-ml three-neck flask was charged with
4-((3-methacrylamidepropyl)dimethylammonio)butane-1-sulfonate (5.17 g),
vinylphosphonic acid (from BASF) (4.53 g), an aqueous solution of 15.0%
by weight of
N-(3-(2-(2-(3-aminopropoxy)ethoxy)ethoxy)propyl)methacrylamide
monophosphate (23.5 g), and distilled water (30 g), and the mixture was
heated with stirring for 10 minutes at 60° C. under a stream of
nitrogen gas. Then, the polymerization initiator VA-046B (from Wako Pure
Chemical Industries, Ltd.) (0.3 g) was dissolved in distilled water (20
g), and added dropwise over 3 hours. Then, VA-046B (0.3 g) was added
again, and the mixture was heated at 80° C. for hours, and then
cooled. The resulting polymer solution was adjusted to pH 9.7 by adding
NaOH. Then, 0.1 g of 4-OH TEMPO (from Tokyo Chemical Industry Co., Ltd.)
was added, and the mixture was heated to 55° C., and methacrylic
anhydride (from Aldrich) (10.0 g) was added dropwise over 1 hour. After
completion of the dropwise addition, the mixture was kept at 55°
C. for 6 hours. Then, ethyl acetate (250 g) was added, and the lower
layer was collected. To the collected lower layer was added 15 g of the
ion exchange resin Amberlyst R15 (from Aldrich), and the mixture was
stirred at room temperature for 2 hours, and then Amberlyst R15 was
removed by filtration to give an aqueous solution of specific polymer
compound P-1-54. The weight average molecular weight (Mw) of the
resulting specific polymer compound P-1-4 was determined to be 10,000 by
Gel Permeation Chromatography (GPC) using polyethylene glycol as
standard. Other specific polymer compounds of the present invention were
also synthesized in the same manner except that the monomer components of
the repeating unit in the synthesis example above were changed, the type
and amount of the reactive reagent used in the amino substitution
reaction and that an existing synthesis method was used, if desired.

Example B

Lithographic Printing Plates

(1) Preparation of Lithographic Printing Plate Precursors

[Preparation of Aluminum Substrate 1]

[0410] An aluminum plate having a thickness of 0.3 mm (quality: JIS A1050)
was degreased using an aqueous solution of 10% by mass of sodium
aluminate at 50° C. for 30 seconds to remove the rolling oil on
the surface, and then grained on the aluminum surface using three nylon
brushes containing bunches of bristles having a diameter of 0.3 mm and an
aqueous suspension of a pumice having a median diameter of 25 μm
(specific gravity 1.1 g/cm3), and thoroughly washed with water. This
plate was etched by immersion in an aqueous solution of 25% by mass of
sodium hydroxide at 45° C. for seconds, and washed with water, and
then further immersed in an aqueous solution of 20% by mass of nitric
acid for seconds at 60° C., and washed with water. The amount of
the grained surface etched here was about 3 g/m2.

[0411] Then, the plate was continuously subjected to an electrochemical
surface-roughening treatment using 60 Hz AC voltage. The electrolyte was
an aqueous solution of 1% by mass of nitric acid (containing 0.5% by mass
of aluminum ions) at a temperature of 50° C. The electrochemical
surface-roughening treatment took place using a carbon electrode as a
counter electrode with an AC power supply generating a trapezoidal wave,
TP (the time until the current value reaches a peak from zero)=0.8 msec,
duty ratio 1:1. An auxiliary ferrite anode was used. The peak current
density was 30 A/dm2, and 5% of the current from the power supply
was shunted to the auxiliary anode.

The quantity of electricity in the electrolysis in nitric acid was 175
C/dm2 when the aluminum plate was used as a cathode. Then, the plate
was washed with water by spraying.

[0412] Then, the plate was subjected to an electrochemical
surface-roughening treatment in the same manner as the electrolysis in
nitric acid except that an aqueous solution of 0.5% by mass of
hydrochloric acid (containing 0.5% by mass of aluminum ions) was used as
an electrolyte at a temperature of 50° C. and the quantity of
electricity was C/dm2 when the aluminum plate was used as a cathode,
and then the plate was washed with water by spraying. This aluminum plate
was treated in an aqueous solution of 15% by mass of sulfuric acid
(containing 0.5% by mass of aluminum ions) as an electrolyte at a current
density of 15 A/dm2 to form an anodic oxide coating of 2.5 g/m2
using a DC power supply, then washed with water, and dried to prepare
aluminum substrate 1.

The center line average roughness (Ra) of the substrate obtained in this
manner was determined to be 0.51 μm using a needle having a diameter
of 2 μm.

[0413] [Preparation of Aluminum Substrate 2]

The aluminum substrate 1 was treated in an aqueous solution of 1% by mass
of sodium silicate at 20° C. for 10 seconds to prepare aluminum
substrate 2. The surface roughness was determined to be 0.54 μm
(expressed as Ra according to JIS B0601).

[0414] [Preparation of Aluminum Substrate 3]

An aluminum plate having a thickness of 0.24 mm (quality 1050, temper
designation H16) was degreased by immersion in a 5% aqueous sodium
hydroxide solution kept at 65° C. for 1 minute, and then washed
with water. This aluminum plate was neutralized by immersion in a 10%
aqueous hydrochloric acid solution kept at 25° C. for 1 minute,
and then washed with water. Then, this aluminum plate was
surface-roughened by AC in an aqueous solution of 0.3% by mass of
hydrochloric acid at 25° C. under the conditions of a current
density of 100 A/dm2 for 60 seconds, and then desmutted in a 5%
aqueous sodium hydroxide solution kept at 60° C. for 10 seconds.
This aluminum plate was subjected to an anodic oxidation treatment in a
1.5% aqueous sulfuric acid solution at 25° C. under conditions of
a current density of 10 A/dm2 and voltage 15 V for 1 minute to
prepare an aluminum substrate. The surface roughness was determined to be
0.44 μm (expressed as Ra according to JIS B0601).

[0415] [Formation of Primer Layer 1]

On the aluminum substrates 1 to 3, a coating solution for primer layer 1
having the composition shown below was applied using a bar coater, and
dried at 100° C. for 1 minute to form primer layer 1. The coating
mass of primer layer 1 was 12 mg/m2 after drying.

[0416] <Coating Solution for Primer Layer 1>

TABLE-US-00001
One of the specific polymer compounds described in 0.50 g
Table 1 and Table 2 or the polymer compounds for
comparison shown below
Methanol 90.0 g
Pure water 10.0 g

[Formation of Photosensitive Layer 1-1]

[0417] A coating solution for photosensitive layer 1-1 having the
composition shown below was applied on the primer layer 1 using a bar
coater, and then dried in an oven at 90° C. for seconds to form
photosensitive layer 1-1 having a coating mass of 1.3 g/m2 after
drying.

A coating solution for photosensitive layer 1-2 having the composition
shown below was applied on the primer layer using a bar coater, and then
dried in an oven at 90° C. for 60 seconds to form photosensitive
layer 1-2 having a coating mass of 1.3 g/m2 after drying.

A coating solution for photosensitive layer 1-3 having the composition
shown below was applied on the primer layer using a bar coater, and then
dried in an oven at 100° C. for 60 seconds to form photosensitive
layer 1-3 having a coating mass of 1.0 g/m2 after drying. The
coating solution for photosensitive layer 1-3 was prepared by mixing the
sensitizer solution (1) and hydrophobizing solution (1) shown below and
stirring the mixture immediately before it was applied.

[0424] (Preparation of an Aqueous Dispersion of Hydrophobization Precursor
(1))

A 1000-ml four-neck flask equipped with a stirrer, a thermometer, a
dropping funnel, a nitrogen inlet, and a reflux condenser was charged
with 350 mL of distilled water under deoxygenation by nitrogen gas
purging and heated until the internal temperature reached 80° C.
To this were added 1.5 g of sodium dodecylsulfate as a dispersant, and
0.45 g of ammonium persulfide as an initiator, and then a mixture of 45.0
g of glycidyl methacrylate and 45.0 g of styrene was added dropwise via
the dropping funnel over about one hour. After completion of the dropwise
addition, the reaction was continued for 5 hours, and then unreacted
monomers were removed by steam distillation. Then, the mixture was cooled
and adjusted to pH 6 with aqueous ammonia, and finally pure water was
added to reduce non-volatiles to 15% by mass, thereby giving an aqueous
dispersion of hydrophobization precursor (1) consisting of polymer
microparticles. The particle size distribution of the polymer
microparticles had a maximum at a particle size of nm.

[0425] The particle size distribution was determined by taking an electron
micrograph of the polymer microparticles and measuring the particle size
of a total of 5000 microparticles on the photograph, and plotting the
frequency of appearance of each of 50 particle sizes on a logarithmic
scale from the maximum to zero of the measured particle sizes. The
particle sizes of nonspherical particles were determined as the particle
sizes of spherical particles having the same particle areas on the
photograph.

[0426] [Formation of Protective Layer 1]

A coating solution for protective layer 1 having the composition shown
below was applied using a bar coater at a coating mass of 0.75 g/m2
after drying, and then dried at 125° C. for 70 seconds to form
protective layer 1.

A coating solution for protective layer 2 having the composition shown
below was applied using a bar coater at a coating mass of 0.75 g/m2
after drying, and then dried at 125° C. for 70 seconds to form
protective layer 2.

[0430] (Preparation of a Dispersion of Inorganic Laminar Compound (1))

[0431] To 193.6 g of ion exchange water was added 6.4 g of synthetic mica
Somasif ME-100 (from Co-op Chemical Co., Ltd.), and the mixture was
dispersed using a homogenizer until the average particle size (by laser
scattering) reached 3 μm to prepare a dispersion of inorganic laminar
compound (1). The resulting dispersed particles had an aspect ratio of or
more.

[0433] In Table 1 and Table 2, specific polymer compounds P-1-1 to P-1-56
represent specific examples of copolymers (A) of the present invention.
The polymer compounds R-1-1 to R-1-5 for comparative examples used in
lithographic printing plate precursors B-1-1 to B-1-10 are compounds for
comparison having structures shown below.

##STR00131##

[0434] (2) Evaluation of Lithographic Printing Plate Precursors

[Exposure, Development and Printing]

[0435] Various lithographic printing plate precursors shown in Tables 3 to
5 below were image-exposed using Violet semiconductor laser platesetter
Vx9600 (incorporating an InGaN semiconductor laser (emission wavelength
405 nm±10 nm/output 30 mW)) from FUJIFILM Electronic Imaging Ltd.
(FFEI). The image exposure was performed using an FM screen (TAFFETA 20)
from Fujifilm Corporation at a resolution of 2,438 dpi and a surface
exposure dose of 0.05 mJ/cm2 to attain a dot area fraction of 50%.
Then, the plate precursors were preheated at 100° C. for 30
seconds, and then developed using each developer shown below in an
automatic developing machine having a structure as shown in FIG. 1. The
automatic developing machine was provided with one brush roll of 50 mm in
outside diameter including polybutylene terephthalate bristles (bristle
diameter 200 μm, bristle length 17 mm) and rotated in the same
direction as the feed direction at 200 rpm (a peripheral speed of 0.52
m/sec at the end of the brush). The temperature of the developer was
30° C. The lithographic printing plate precursors were fed at a
feed speed of 100 cm/min. The development was followed by drying in a
drying part. The drying temperature was 80° C. When developer 2
was used, the drying after development was preceded by washing with
water.

[0436] The compositions of developers 1 to 5 are shown below. In the
compositions below, Newcol B13 (from NIPPON NYUKAZAI CO., LTD.) is
polyoxyethylene β-nephthyl ether (average number of oxyethylene
groups n=13), and gum arabic has a mass average molecular weight of
200,000.

Each lithographic printing plate precursor was evaluated for printing
durability, staining resistance, staining resistance over time and
developability as follows. The results are shown in Tables 3 to 5.

<Printing Durability>

[0444] As the number of prints increased, the ink density on printing
paper decreased because the photosensitive layer gradually wore and
decreased in ink receptivity. In printing plates exposed at the same
exposure dose, printing durability was evaluated by determining the
number of prints when the ink density (reflection density) decreased by
0.1 as compared with the density at the start of printing. The evaluation
of printing durability was reported as the relative printing durability
defined below using Comparative examples 1-1, 1-7 and 1-10 as references
(1.0) respectively in Tables 3 to 5. Higher values of the relative
printing durability indicate higher printing durability. Relative
printing durability=(Printing durability of test lithographic printing
plate precursor)/(Printing durability of reference lithographic printing
plate precursor).

[0445] <Staining Resistance>

After printing was started, the 20th print was sampled to evaluate
staining resistance by the density of the ink deposited on non-image
areas. The ink deposition on non-image areas was reported as a score of
visual evaluation per 75 cm2 because it does not always occur
uniformly. Scores of visual evaluation for ink-deposited area fractions
in non-image areas are as follows: score 10 for 0%, score 9 for more than
0% and 10% or less, score 8 for more than 10% and 20% or less, score 7
for more than 20% and 30% or less, score 6 for more than 30% and 40% or
less, score 5 for more than 40% and 50% or less, score for more than 50%
and 60% or less, score 3 for more than 60% and 70% or less, score 2 for
more than 70% and 80% or less, score 1 for more than 80% and 90% or less,
and score 0 for more than 90% and 100% or less. Higher scores indicate
better staining resistance.

[0446] <Staining Resistance Over Time>

After the lithographic printing plate was prepared, it was left in a
constant temperature and humidity chamber set at 60° C. and a
relative humidity of 60% for three days. This printing plate was used to
evaluate staining resistance over time in the same manner as described
for the evaluation of staining resistance. Higher scores indicate better
staining resistance over time.

[0447] <Developability>

The development process described above was performed at varying feed
speeds, and the cyan density in non-image areas of the resulting
lithographic printing plate was measured by a MacBeth densitometer.
Developability was evaluated by determining the feed speed when the cyan
density in non-image areas equaled to the cyan density in the aluminum
substrate. The evaluation of developability was reported as the relative
developability defined below using Comparative examples 1-1, 1-7 and 1-10
as references (1.0) respectively in Tables 3 to 5. Higher values of the
relative developability indicate higher developability and better
performance.

[0448] Tables 3 to 5 above show that Examples 1-1 to 1-70 and 1-104 to
1-115 using copolymers (A) comprising repeating units complying with
formula (a1-1) were excellent in staining resistance, staining resistance
over time and developability without compromising printing durability.
However, Comparative example 1-1 using polymer compound R-1-1 for
comparative examples solely comprising a repeating unit having a
functional group interacting with the substrate surface and Comparative
examples 1-2, 1-7, and 1-10 using polymer compound R-1-2 for comparative
examples were all shown to be poor in printing durability, staining
resistance, and staining resistance over time. Comparative example 1-3
using polymer compound R-1-3 for comparative examples comprising a
repeating unit having a functional group interacting with the substrate
surface and a side chain repeating unit having a polymerizable group in a
side chain of the repeating unit but lacking a specific linking group and
not complying with formula (a1-1) was shown to be poor in staining
resistance and staining resistance over time.

Comparative examples 1-4, 1-8, and 1-11 using polymer compound R-1-4 for
comparative examples comprising a repeating unit having a functional
group interacting with the substrate surface and a repeating unit
containing a hydrophilic group having a zwitterionic structure in a side
chain but lacking a polymerizable group in a side chain of any repeating
unit were all shown to be very poor in printing durability and also poor
in the balance between staining resistance and staining resistance over
time. Comparative examples 1-5, 1-9, and 1-12 using polymer compound
R-1-5 for comparative examples comprising a repeating unit having a
functional group interacting with the substrate surface and a side chain
repeating unit having a polymerizable group in a side chain of the
repeating unit but lacking a specific linking group and not complying
with formula (a1-1) were shown to be poor in staining resistance and
staining resistance over time.

[0449] <Exposure, Development and Printing>

Various lithographic printing plate precursors shown in Tables 6 and 7
were image-exposed at a 50% tint using Trendsetter 3244VX from Creo
(incorporating a water-cooled 40 W infrared semiconductor laser (830 nm))
under conditions of an output power of 9 W, an external drum rotational
speed of 210 rpm, and a resolution of 2,400 dpi. Then, the image was
developed using developer 1 or 4 in an automatic developing machine
having a structure shown in FIG. 2 with heater settings that allow the
plate surface to reach a temperature of 100° C. in the preheating
part and at a feed speed that allows an immersion time in the developer
(developing time) of 20 seconds.

[0451] Each lithographic printing plate precursor was evaluated for
printing durability, staining resistance, staining resistance over time,
and developability in the same manner as in Example 1-1. The evaluation
of printing durability and developability was made by using Comparative
examples 1-13 and 1-15 as reference (1.0) in Tables 6 and 7,
respectively. The results are shown in Tables 6 and 7.

[0452] Tables 6 and 7 show that Examples 1-71 to 1-92 and 1-116 to 1-121
using copolymers (A) comprising repeating units complying with formula
(a1-1) were excellent in staining resistance, staining resistance over
time and developability without compromising printing durability.
However, Comparative examples 1-13 and 1-15 using polymer compound R-1-4
for comparative examples comprising a repeating unit having a functional
group interacting with the substrate surface and a repeating unit
containing a hydrophilic group having a zwitterionic structure in a side
chain but lacking a polymerizable group in a side chain of any repeating
unit were shown to be poor especially in staining resistance and staining
resistance over time. They also remained unsatisfactory in printing
durability and developability.

Comparative examples 1-14 and 1-16 using polymer compound R-1-5 for
comparative examples comprising a repeating unit having a functional
group interacting with the substrate surface and a repeating unit having
a polymerizable group in a side chain of the repeating unit but lacking a
specific linking group and not complying with formula (a1-1) were shown
to be poor in staining resistance and staining resistance over time. They
also remained unsatisfactory in developability.

[0453] <Exposure, Development and Printing>

Various lithographic printing plate precursors shown in Table 8 below
were exposed using Luxel PLATESETTER T-6000III incorporating an infrared
semiconductor laser from Fujifilm Corporation, under conditions of an
external drum rotational speed of 1000 rpm, a laser output of 70%, and a
resolution of 2400 dpi. The image formed by exposure included solid areas
and halftone areas produced by 20 μm dot FM screening. The exposed
lithographic printing plate precursors were mounted on the printing press
LITHRONE 26 from KOMORI Corporation without developing the image. The
image was developed on press with a dampening solution of Ecolity-2 (from
Fujifilm Corporation)/tap water=2/98 (volume ratio) and Values-G(N) black
ink (from DIC Corporation) by supplying the dampening solution and the
ink according to the standard automatic print starting mode of LITHRONE
26, followed by printing on 100 sheets of Tokubishi Art paper (76.5 kg)
at a printing speed of 10000 sheets/hr.

[0454] [Evaluation]

Each lithographic printing plate precursor was evaluated for on-press
developability and printing durability as follows. Staining resistance
and staining resistance over time were evaluated as described in Example
1-1. The results are shown in Table below 8.

<On-Press Developability>

[0455] On-press developability was evaluated by determining the number of
sheets of printing paper required until on-press development of non-image
areas of the photosensitive layer was completed and the ink was no more
transferred to the non-image areas.

[0456] <Printing Durability>

After the evaluation of on-press developability, printing was further
continued. As the number of prints increased, the ink density on the
prints decreased because the photosensitive layer gradually wore.
Printing durability was evaluated by determining the number of prints at
the end of printing when the dot area fraction of halftone dots produced
by FM screening in a print measured by a Gretag densitometer decreased by
5% as compared with the value measured in the 100th print. The evaluation
of printing durability was reported as the relative printing durability
defined below using Comparative example 1-17 as reference (1.0). Higher
values of the relative printing durability indicate higher printing
durability.

[0457] Table 8 above shows that Examples 1-93 to 1-103 and 1-122 to 1-124
using copolymers (A) comprising a repeating unit complying with formula
(a1-1) were excellent in staining resistance, staining resistance over
time and on-press developability without compromising printing
durability.

However, Comparative example 1-17 using polymer compound R-1-4 for
comparative examples comprising a repeating unit having a functional
group interacting with the substrate surface and a repeating unit
containing a hydrophilic group having a zwitterionic structure in a side
chain but lacking a polymerizable group in a side chain of any repeating
unit was shown to be poor in staining resistance, and staining resistance
over time. Moreover, it was also shown to be inferior to the other
Examples in the evaluation of developability and the number of sheets
developed on press. Comparative example 1-18 using polymer compound R-1-5
for comparative examples comprising a repeating unit having a functional
group interacting with the substrate surface and a repeating unit having
a polymerizable group in a side chain of the repeating unit but lacking a
specific linking group and not complying with formula (a1-1) was shown to
be poor in staining resistance and staining resistance over time.
Further, it was also shown to be inferior to the other Examples in the
evaluation of the number of sheets developed on press.

Example C

Synthesis Example of a Copolymer

Synthesis Example 1

Synthesis of a Compound of the Present Invention (P-2-21)

[0458] (1) Synthesis of N-aminoethyl methacrylamide

[0459] To an ice-cooled solution of 24.04 g (0.4 mol) of ethylenediamine
dissolved in 100 ml of methanol and 96 g of distilled water is added 104
g (0.52 mol) of 5.0 M hydrochloric acid. While the temperature is kept at
-10° C., 61.65 g of methacrylic anhydride is added dropwise, and
after completion of the dropwise addition, the mixture is stirred at
-10° C. for 2 hours. Then, the mixture is extracted with ml of
ethyl acetate and the aqueous layer is collected. To the collected
aqueous layer is added 21 g (0.52 mol) of sodium hydroxide, and the
precipitated white crystals are removed by filtration and extracted with
400 ml of acetonitrile. The acetonitrile solution is dried over 40 g of
magnesium sulfate for 2 hours, and then acetonitrile is distilled off to
give 14.4 g of N-aminoethyl methacrylamide (yield 28%).

[0461] A 200-ml flask equipped with a condenser and a stirrer was charged
with 27.32 g of distilled water and heated to 55° C. under a
stream of nitrogen gas. A solution consisting of 0.71 g of N-aminoethyl
methacrylamide synthesized above, 11.1 g of the aqueous solution of LIGHT
ESTER P-2-1M synthesized above, 3.87 g of 3-sulfonatopropyl
[2-(methacryloyloxy)ethyl]dimethylammonium (from Aldrich), 0.32 g of the
polymerization initiator VA046B (from Wako Pure Chemical Industries,
Ltd.), and 9.41 g of distilled water was added dropwise into the 200-ml
flask over 2 hours. After completion of the dropwise addition, the
mixture was stirred at 55° C. for 2 hours, and 0.32 g of the
polymerization initiator VA046B (from Wako Pure Chemical Industries,
Ltd.) was added, and the mixture was further stirred at 55° C. for
2 hours to give a precursor for compound (21). To 50.0 g of an aqueous
solution of the resulting precursor for compound (1) was added 1.38 g of
sodium hydroxide and dissolved, and then the solution was warmed to
40° C. and 4.3 g of Karenz MOI (from Showa Denko K.K.) was added,
and the mixture was stirred at 40° C. for 6 hours. Then, an
aqueous solution obtained by removing precipitated white crystals by
filtration was stirred with 8.83 g of Amberlyst R15 (from Aldrich) at
room temperature for 2 hours, and then Amberlyst R15 was removed by
filtration to give compound (P-2-21). The weight average molecular weight
(Mw) of the resulting compound (P-2-21) was determined to be 150,000 by
Gel Permeation Chromatography (GPC) using polyethylene glycol as
standard. Further, the reaction yield of amino groups was 75% as
determined by the color reaction of amino groups.

[0462] The compound used in this Example was synthesized by changing the
monomer components of the repeating units in the Synthesis example
described above, changing the type and amount of the reactive reagent
used for amino substitution reaction, and further using an existing
synthesis method, if desired.

Example D

(1) Preparation of Lithographic Printing Plate Precursors

[0463] The aluminum substrates used were aluminum substrates 1 to of
Example B. A coating solution for primer layer 2 having the composition
shown below was applied on each of the aluminum substrate 1 to 3 using a
bar coater and dried at 100° C. for 1 minute to form a primer
layer. The coating mass of the primer layer was 12 mg/m2 in each
case.

[0464] <Coating Solution for Primer Layer 2>

TABLE-US-00021
One of the copolymers of the present invention 0.50 g
described in Table 9 or Table 10 or the polymer
compounds for comparison shown below
Methanol 450 g
Pure water 50 g

[0465] [Formation of Photosensitive Layer 2-1]

A coating solution for photosensitive layer 2-1 having the composition
shown below was applied on the primer layer using a bar coater, and then
dried in an oven at 90° C. for 60 seconds to form photosensitive
layer 2-1 having a coating mass of 1.3 g/m2 after drying.

A coating solution for photosensitive layer 2-2 having the composition
shown below was applied on the primer layer using a bar coater, and then
dried in an oven at 90° C. for 60 seconds to form photosensitive
layer 2-2 having a coating mass of 1.3 g/m2 after drying.

[0470] A coating solution for photosensitive layer 2-3 having the
composition shown below was applied on the primer layer 2 using a bar
coater, and then dried in an oven at 125° C. for seconds to form
photosensitive layer 2-3 having a coating mass of 1.4 g/m2 after
drying. The coating solution for photosensitive layer 2-3 was prepared by
mixing the sensitizer solution (1) and hydrophobizing solution (1) shown
below and stirring the mixture immediately before it was applied.

[0477] Exposure, development and printing were performed by using various
lithographic printing plate precursors shown in Table 11 and Table 12
below in the same manner as in Example B. The developer used was also any
one of developers 1 to shown in Example B.

[0479] Printing durability was evaluated in the same manner as in Example
B. In Table 11 and Table 12 below, the results were reported as the
relative printing durability defined below using Examples 2-6 and 2-24 as
references (1.0) respectively.

[0480] <Staining Resistance>

Staining resistance was evaluated in the same manner as in Example B.

[0481] <Developability>

Developability was evaluated in the same manner as in Example B. The
evaluation of developability was reported as the relative developability
defined below using Examples 2-6 and 2-24 as references (1.0)
respectively in Table 11 and Table 12 below. Higher values of the
relative developability indicate higher developability and better
performance.

[0482] <Printing Durability with UV Inks>

In the evaluation of printing durability described above, the dampening
water (EU-3 (an etching solution from Fujifilm
Corporation)/water/isopropyl alcohol=1/89/10 (volume ratio)) and
TRANS-G(N) black ink (from DIC Corporation) were replaced by a 2 vol %
aqueous solution of the dampening solution IF102 (from Fujifilm
Corporation) and BEST CURE UV-BF-WRO Standard Color Black ink (from T&K
TOKA Co., Ltd.), and after the dampening solution and the ink were
supplied, printing was performed at a printing speed of 6000 sheets/hr.
Printing durability with UV inks was evaluated by determining the number
of prints when the image density of a print decreased by 5% as compared
with the density at the start of printing, and reported as the relative
printing durability with UV inks defined below using Examples 2-6 and
2-24 as references (1.0), respectively in Table 11 and Table 12. Higher
values of the relative printing durability with UV inks indicate higher
printing durability with UV inks.

In the evaluation of printing durability described above, the dampening
water (EU-3 (an etching solution from Fujifilm
Corporation)/water/isopropyl alcohol=1/89/10 (volume ratio)) and
TRANS-G(N) black ink (from DIC Corporation) were replaced by a 4 vol %
aqueous solution of the dampening solution IF102 (from Fujifilm
Corporation) and Values G black ink (from DIC Corporation), and the plate
surface was wiped with Multicleaner (from Fujifilm Corporation) every
5000 sheets. Printing was performed on a woodfree paper, and chemical
resistance was evaluated by determining the number of prints when the
density of the solid image was visually observed to begin to decrease,
and reported as the relative chemical resistance defined below using
Examples 2-6 and 2-24 as references (1.0), respectively in Table 11 and
Table 12. Higher values of the relative chemical resistance indicate
higher chemical resistance.

[0484] Table 11 and Table 12 above show that the lithographic printing
plate precursors using copolymers (A) of the present invention can
provide lithographic printing plates excellent in printing durability and
printing durability with UV inks without compromising staining resistance
and developability. Moreover, the lithographic printing plate precursors
of the present invention were also excellent in chemical resistance.
Among the lithographic printing plate precursors of the present
invention, A-2-1 to A-2-16, A-2-18 to A-2-29, A-2-31 to A-2-37 and A-2-39
were shown to especially strike an excellent balance among printing
durability, staining resistance, developability and printing durability
with UV inks, and the lithographic printing plates obtained therefrom
were also shown to provide an excellent balance among printing
durability, staining resistance, developability, printing durability with
UV inks and chemical resistance. In Example 2-7, printing durability,
staining resistance, printing durability with UV inks, and chemical
resistance were evaluated by using lithographic printing plate A-2-7 and
developer 1 to find that they were good.

However, the polymer compounds for comparative examples comprising a side
chain repeating unit lacking a specific linking group and not complying
with formula (a1-1) did not produce advantages of the present invention.
Specifically, Comparative examples 2-1, 2-4, 2-6, 2-8 and 2-11 using
polymer compound R-2-1 for comparative examples were shown to be poor in
staining resistance and developability. Comparative examples 2-2, 2-9 and
2-12 using polymer compound R-2-2 for comparative examples were shown to
be poor in printing durability, staining resistance, developability and
printing durability with UV inks even though this polymer compound R-2-2
comprises a repeating unit having a functional group interacting with the
substrate surface. Comparative examples 2-3, 2-5, 2-6, 2-10 and 2-13
using polymer compound R-2-3 for comparative examples were shown to be
poor in developability. The comparative examples using polymer compounds
R-2-4 and R-2-5 for comparative examples were shown to be poor in
printing durability, printing durability with UV inks, and chemical
resistance.

[0485] [Exposure, Development and Printing]

Various lithographic printing plate precursors shown in Table 13 below
were image-exposed using Trendsetter 3244VX from Creo (incorporating a
water-cooled 40 W infrared semiconductor laser) under conditions of an
output power of 9 W, an external drum rotational speed of 210 rpm, and a
resolution of 2,400 dpi. Within 30 seconds after then, the precursors
were preheated at 100° C. for 30 seconds, and then developed using
developer 1 in the same manner as in

Example B

[0486] The lithographic printing plates obtained were used to evaluate
printing durability, staining resistance, developability, printing
durability with UV inks and chemical resistance in the same manner as in
Example B. Example 2-40 was used as a reference for relative evaluations.
The results are shown in Table 13 below.

[0487] Table 13 above show that the lithographic printing plate precursors
using copolymers (A) of the present invention can also provide
lithographic printing plates excellent in printing durability, printing
durability with UV inks and chemical resistance without compromising
staining resistance and developability when they were image-exposed using
infrared light. Moreover, the lithographic printing plate precursors of
the present invention were also excellent in chemical resistance. Among
the lithographic printing plate precursors of the present invention,
Examples 2-40 to 2-45 and 2-47 were shown to especially strike an
excellent balance among printing durability, staining resistance,
developability and printing durability with UV inks, and the lithographic
printing plates obtained therefrom were also shown to provide an
excellent balance among printing durability, staining resistance,
developability, printing durability with UV inks and chemical resistance.

However, the polymer compounds for comparative examples comprising a side
chain repeating unit lacking a specific linking group and not complying
with formula (a1-1) did not produce advantages of the present invention.
Specifically, Comparative example 2-14 using polymer compound R-2-1 for
comparative examples was shown to be poor in staining resistance and
developability. Comparative example 2-15 using polymer compound R-2-2 for
comparative examples was shown to be poor in printing durability,
staining resistance, developability and printing durability with UV inks.
Comparative example 2-16 using polymer compound R-2-3 for comparative
examples was shown to be poor in developability. The comparative examples
using polymer compound R-2-4 or R-2-5 for comparative examples were shown
to be poor in printing durability, printing durability with UV inks, and
chemical resistance.